Your answer would be 16 sides.
This is because, to find the sum of the interior angles in a polygon, the formula is (n - 2) × 180, with n being the number of sides. Because we know the sum of interior angles already, we can write it as an equation to solve:
(n - 2) × 180 = 2520
÷ 180
n - 2 = 14
+ 2
n = 16
I hope this helps!