If you mean the SI Unit of GPE, the answer is J for Joules.
if that's not the question being asked, i would need a little more elaboration please :)
The answer is as voltage increases current increases and therefore resistance would remain constant
Air pressure pushing in on the balloon decreases as the balloon rises.
Energy Density = 1/2 × ε(0) × (V/d)^2
V = 100, d = 0.01, ε(0) = 8.85 x 10^-12