The area of a square is found by multiplying length and width, (which just so happen to be the same number) and the unit of measurement and put the power of 2 at the end (^2).
For example, if a square's length is 4cm, then you can assume the width is going to be 4cm. Finding area, you multiply 4 and 4 to get 16, and the unit of measurement (cm) and square it (^2). Thus meaning this answer would be 16cm^2.
I hope this helps!