how can i fix this statement

here is my code

from tkinter import *
# Main window

App = Tk()
App.title("Converter")
App.geometry('360x180')
# Menu

kind = ['Temperature', 'Length', 'Weight']
all = StringVar()
all_menu = OptionMenu(App, all, *kind)
all_menu.grid(row=0, column=1, pady=5)

# Get index

index = all.get()
if index == 'Temperature' :
    scales = ['Fahrenheit','Celsius']
elif index == 'Length' :
    scales = ['Mile','Kilometer']
else: 
    scales = ['Pound','Kilogram']

# The scale of the length to be used for conversion

_from = StringVar()
from_menu = OptionMenu(App, _from, *scales)
from_menu.grid(row=1, column=1, pady=5)

# In between label

lbl = Label(App, text=' convert to ')
lbl.grid(row=1, column=2, pady=5)

# The scale of the length to convert the value to

to_ = StringVar()
to_menu = OptionMenu(App, to_, *scales)
to_menu.grid(row=1, column=3, pady=5)

# Entry pre-label

numL = Label(App, text='Enter: ')
numL.grid(row=2, column=0, columnspan=1, pady=5)

# Entry field 

numE = Entry(App)
numE.grid(row=2, column=1, columnspan=1, pady=5)

# In between Entry field and Converter function

equal = Label(App, text=' = ')
equal.grid(row=2, column=2, pady=5)

# Converter temperature function

def Convert_Temperature():
    froM = _from.get()
    tO = to_.get()
    num = int(numE.get())

    if froM == 'Fahrenheit' and tO == 'Celsius':
        converted_num = (num - 32) * 5 / 9
    elif froM == 'Celsius' and tO == 'Fahrenheit':
        converted_num = (num * 9 / 5) + 32 
    else:
        converted_num = num

    conv_numL = Label(App, text=round(converted_num, 4), width=10)
    conv_numL.grid(row=2, column=3, pady=5)

# Converter length function

def Convert_Length():
    froM = _from.get()
    tO = to_.get()
    num = int(numE.get())

    if froM == 'Mile' and tO == 'Kilometer':
        converted_num = num * 1.609
    elif froM == 'Kilometer' and tO == 'Mile':
        converted_num = num / 1.609  
    else:
        converted_num = num

    conv_numL = Label(App, text=round(converted_num, 4), width=10)
    conv_numL.grid(row=2, column=3, pady=5)

# Converter weight function

def Convert_Weight():
    froM = _from.get()
    tO = to_.get()
    num = int(numE.get())

    if froM == 'Pound' and tO == 'Kilogram':
        converted_num = num / 2.205
    elif froM == 'Kilogram' and tO == 'Pound':
        converted_num = num * 2.205  
    else:
        converted_num = num

    conv_numL = Label(App, text=round(converted_num, 4), width=10)
    conv_numL.grid(row=2, column=3, pady=5)

# Convert button

if index == 'Temperature':
    conB = Button(App, text='Convert', command=Convert_Temperature)
elif index == 'Length':
    conB = Button(App, text='Convert', command=Convert_Length)
else:
    conB = Button(App, text='Convert', command=Convert_Weight)
conB.grid(row=3, column=1, pady=5)

# Clear text function

def clear_text():
    numE.delete(0, END)
    _from.set("")
    to_.set("")
    conv_numL = Label(App, text="", width=10)
    conv_numL.grid(row=2, column=3, pady=5)

# Clear text button

btn = Button(App, text="Restart", command=clear_text)
btn.grid(row=3, column=3, pady=5)

App.mainloop()

# Label -> print text
# Grid -> Locate
# Entry -> table