V = Bh, and B has to be "something" squared since the base is a square.
The factors of 16 that are perfect squares themselves are 1, 4 and 16.
h is going to be x plus something because squaring the dimensions of the base gives us a positive number and we have a positive 16 as our final result.
So, our options are...
(x - 1)(x - 1)(x + 16)
(x + 1)(x + 1)(x + 16)
(x - 2)(x - 2)(x + 4)
(x + 2)(x + 2)(x + 4)
(x - 4)(x - 4)((x + 1)
(x + 4)(x + 4)(x + 1)
All we have to do is add the constants to see which adds up to 8. -1 + (-1) + 16 ≠ 8, so that's not it.
I bet you can find it from here!