I am not sure how to do this problem

Convert the units. 15 yd2 = _____ ft2

I assume you're trying to say

15 sq. yards is equal to X sq. feet.

To solve, you need to know that 1 sq. yard = 9 sq. feet (there are 3 feet to a yard).

With that information, you should be able to solve.....

If not, the answer is 135 sq. feet