Could someone please assist me​

None of those are technically correct. 9.7 x 104 is actually 1,008.8, but if that answer was a choice, it would be that one. if you meant 9.7 times maybe a thousand or more or divided by 10 or more, than the answer choices would be correct, but other than that, they actually arent.

Use pythagorean’s theorem and find the missing side lengths of the two smaller triangles and add them together
13^2 - 12^2 = 5
15^2 - 12^2 = 9
5+9 = 14
14 is the length of each side of the square
14^2 + 14^2 = 19.8
19.8 is the diagonal length of the inside if the square