Energy of Inductor is given by the formula:
Energy = (1/2) * L*I^2 (*where L=inductance, I=current)
Before we can determine the energy, we need to find L
L = (permeability of free space * N^2 * A) / l (*where N=number turns, A=area = pi*r^2, l=length)
After solving for L, you can then plug back into the first equation to solve for energy.