Getting any variable into any position in table

I am still pretty new to JavaScript and trying to improve my very basic skills. I've built a simple table where you enter the car reg and the car name pops up, you enter the miles left, and the miles needed and it calculates how many hours until you need to charge.

Currently you have to enter car 1 reg number in to the first row, car 2 in to the 2nd car 3 in to third etc and was wondering if there is a way to rewrite the if statements so that you can type any car reg in any order and it still pulls up the correct car name.

I tried putting the car reg's in to an array and calling the array to check (the var is still there) but I couldn't get it to work.

Here is the full code on JSFiddle: https://jsfiddle.net/Coxy/1r30xgjc/1/

Here are the if statements :

// Getting name based on registration 

var car1 = "Little White";
var car2 = "Little Grey";
var car3 = "The Tango";
var car4 = "The Gandalf";
var car5 = "Aqua";
var car6 = "Big Red";

var car_1_reg = "NP60UQQ";
var car_2_reg = "NP60UQS";
var car_3_reg = "NP60UQT";
var car_4_reg = "NP60UQU";
var car_5_reg = "NP60UQV";
var car_6_reg = "NP60UQW";

var reg = [car_1_reg,car_2_reg,car_3_reg,car_4_reg,car_5_reg,car_6_reg];

var car_name_1 = document.getElementById('car-1-name');
var car_1_charge = document.getElementById('car-1-charge-needed');
$(".confirm").click(function() {
    var car_reg_1 = $("#car-1-reg").val();
    var a =  parseInt(document.getElementById('car-1-cmra').textContent, 10);
    var b =  parseInt(document.getElementById('car-1-mtnc').textContent, 10);
    var miles = Math.ceil((b - a) / 44);  
    console.log(miles)
    if (car_reg_1 != car_1_reg) {
        car_name_1.innerText = 'Not a valid Registration';
        car_1_charge.textContent = "Please enter a valid registration";
    } else if (car_reg_1 = car_1_reg && ( isNaN(a) )) {
        car_name_1.textContent = car1;
        car_1_charge.textContent = "Please enter the current miles left";
    } else if (car_reg_1 = car_1_reg && ( isNaN(b) )) {
        car_name_1.textContent = car1;
        car_1_charge.textContent = "Please enter the miles needed";
    } else {
        car_name_1.textContent = car1;
        car_1_charge.textContent = miles;
    }
});

var car_name_2 = document.getElementById('car-2-name');
var car_2_charge = document.getElementById('car-2-charge-needed');
$(".confirm").click(function() {
    var car_reg_2 = $("#car-2-reg").val();
    var a =  parseInt(document.getElementById('car-2-cmra').textContent, 20);
    var b =  parseInt(document.getElementById('car-2-mtnc').textContent, 20);
    var miles = Math.ceil((b - a) / 44);  
    console.log(miles)
    if (car_reg_2 != car_2_reg) {
        car_name_2.innerText = 'Not a valid Registration';
        car_2_charge.textContent = "Please enter a valid registration";
    } else if (car_reg_2 = car_2_reg && ( isNaN(a) )) {
        car_name_2.textContent = car2;
        car_2_charge.textContent = "Please enter the current miles left";
    } else if (car_reg_2 = car_2_reg && ( isNaN(b) )) {
        car_name_2.textContent = car2;
        car_2_charge.textContent = "Please enter the miles needed";
    } else {
        car_name_2.textContent = car2;
        car_2_charge.textContent = miles;
    }
});

var car_name_3 = document.getElementById('car-3-name');
var car_3_charge = document.getElementById('car-3-charge-needed');
$(".confirm").click(function() {
    var car_reg_3 = $("#car-3-reg").val();
    var a =  parseInt(document.getElementById('car-3-cmra').textContent, 30);
    var b =  parseInt(document.getElementById('car-3-mtnc').textContent, 30);
    var miles = Math.ceil((b - a) / 44);  
    console.log(miles)
    if (car_reg_3 != car_3_reg) {
        car_name_3.innerText = 'Not a valid Registration';
        car_3_charge.textContent = "Please enter a valid registration";
    } else if (car_reg_3 = car_3_reg && ( isNaN(a) )) {
        car_name_3.textContent = car3;
        car_3_charge.textContent = "Please enter the current miles left";
    } else if (car_reg_3 = car_3_reg && ( isNaN(b) )) {
        car_name_3.textContent = car3;
        car_3_charge.textContent = "Please enter the miles needed";
    } else {
        car_name_3.textContent = car3;
        car_3_charge.textContent = miles;
    }
});

var car_name_4 = document.getElementById('car-4-name');
var car_4_charge = document.getElementById('car-4-charge-needed');
$(".confirm").click(function() {
    var car_reg_4 = $("#car-4-reg").val();
    var a =  parseInt(document.getElementById('car-4-cmra').textContent, 40);
    var b =  parseInt(document.getElementById('car-4-mtnc').textContent, 40);
    var miles = Math.ceil((b - a) / 44);  
    console.log(miles)
    if (car_reg_4 != car_4_reg) {
        car_name_4.innerText = 'Not a valid Registration';
        car_4_charge.textContent = "Please enter a valid registration";
    } else if (car_reg_4 = car_4_reg && ( isNaN(a) )) {
        car_name_4.textContent = car4;
        car_4_charge.textContent = "Please enter the current miles left";
    } else if (car_reg_4 = car_4_reg && ( isNaN(b) )) {
        car_name_4.textContent = car4;
        car_4_charge.textContent = "Please enter the miles needed";
    } else {
        car_name_4.textContent = car4;
        car_4_charge.textContent = miles;
    }
});

var car_name_5 = document.getElementById('car-5-name');
var car_5_charge = document.getElementById('car-5-charge-needed');
$(".confirm").click(function() {
    var car_reg_5 = $("#car-5-reg").val();
    var a =  parseInt(document.getElementById('car-5-cmra').textContent, 50);
    var b =  parseInt(document.getElementById('car-5-mtnc').textContent, 50);
    var miles = Math.ceil((b - a) / 44);  
    console.log(miles)
    if (car_reg_5 != car_5_reg) {
        car_name_5.innerText = 'Not a valid Registration';
        car_5_charge.textContent = "Please enter a valid registration";
    } else if (car_reg_5 = car_5_reg && ( isNaN(a) )) {
        car_name_5.textContent = car5;
        car_5_charge.textContent = "Please enter the current miles left";
    } else if (car_reg_5 = car_5_reg && ( isNaN(b) )) {
        car_name_5.textContent = car5;
        car_5_charge.textContent = "Please enter the miles needed";
    } else {
        car_name_5.textContent = car5;
        car_5_charge.textContent = miles;
    }
});

var car_name_6 = document.getElementById('car-6-name');
var car_6_charge = document.getElementById('car-6-charge-needed');
$(".confirm").click(function() {
    var car_reg_6 = $("#car-6-reg").val();
    var a =  parseInt(document.getElementById('car-6-cmra').textContent, 60);
    var b =  parseInt(document.getElementById('car-6-mtnc').textContent, 60);
    var miles = Math.ceil((b - a) / 44);  
    console.log(miles)
    if (car_reg_6 != car_6_reg) {
        car_name_6.innerText = 'Not a valid Registration';
        car_6_charge.textContent = "Please enter a valid registration";
    } else if (car_reg_6 = car_6_reg && ( isNaN(a) )) {
        car_name_6.textContent = car6;
        car_6_charge.textContent = "Please enter the current miles left";
    } else if (car_reg_6 = car_6_reg && ( isNaN(b) )) {
        car_name_6.textContent = car6;
        car_6_charge.textContent = "Please enter the miles needed";
    } else {
        car_name_6.textContent = car6;
        car_6_charge.textContent = miles;
    }
});

As you can see it's a lot of code and I am sure there must be a way so that it does what I need it to, and is shorter?

The end result is to generate a time-table charge schedule based off of the information submitted by the user so that each car is fully charged for the journeys on the following day.

Any pointers or advice is really appreciated, thank you.