How do i check if a certain index of a vector is a specific int?

I need to check a vector for its values at certain indices. After importing strings from a text file into a vector and then converting the imported strings to int I need to check if for example Vector[1] is equal to 4.

I tried if (Vector[1] = 4){...} which didn't work though with the error message "could not convert [...]" (which might be very obvious to most people who read this).