how to create conditional statement with string in Flutter?

i am trying to create an app with flutter on android studio 3.5.2,, everything is fully updated,

the concept is this,, There is a text field, and a Submit button, and within the submit button, three strings/text needs to be valid to get inside,

if somebody inputted a word that wont match it will show, no words exist,

sample,

Strings - philippines, dubai, japan

if { textfield does not match string, Show text hint - Does not match data, }

Else {''' Welcome from "string" }

im still new,, and i know this is not the exact code, but i hope somebody can help me translate this for flutter code,, thank you to whoever will help