I Am Asked To Calculate Rotational Energy Of Each Level & Rotational Energy Difference Between Each Level By Formulae E=h^2/8pi^2I*J(J+1), where J is rational Quantum number, I inertia, * is multiply. They Have Provided J=1,2,3. How To Find, Its Rigid Rotator & inertia is not provided, I WILL BE EXTREMELY THANKFUL FOR RIGHT ANSWER, PLS HELP ME WITH THIS FOR EXAMS

If you aren't told the type of molecule, or any values you can get 'I' from, just state that you don't have this information so have given the results algebraically:
Let A = h^2/(8pi^2I). Then the energy levels are:
For J = 1, E1 = Ax1x(1+1) = 2A
For J = 2, E2 = Ax2x(2+1) = 6A
For J = 3, E3 = Ax3x(3+1) = 12A
The energy level difference are:
For J = 2 to J = 1, E21 = E2  E1 = 6A  2A = 4A
For J = 3 to J = 1, E31 = E3  E1 = 12A  2A = 10A
For J = 3 to J = 2, E321 = E3  E2 = 12A  6A = 6A
If you really want actual values, you can say you have chosen to use hydrogen since no specific figures were provided. For hydrogen I = 4.6x10^48 kgm^2. (e.g. see link  you might find a better reference if you spend some time searching).
A = h^2/(8pi^2I) = (6.63x10^34)^2/(8 x pi^2 x 4.6x10^48) = 3.8x10^21 J
You can then use this value of A to find the actual values, in joules, above.
Let A = h^2/(8pi^2I). Then the energy levels are:
For J = 1, E1 = Ax1x(1+1) = 2A
For J = 2, E2 = Ax2x(2+1) = 6A
For J = 3, E3 = Ax3x(3+1) = 12A
The energy level difference are:
For J = 2 to J = 1, E21 = E2  E1 = 6A  2A = 4A
For J = 3 to J = 1, E31 = E3  E1 = 12A  2A = 10A
For J = 3 to J = 2, E321 = E3  E2 = 12A  6A = 6A
If you really want actual values, you can say you have chosen to use hydrogen since no specific figures were provided. For hydrogen I = 4.6x10^48 kgm^2. (e.g. see link  you might find a better reference if you spend some time searching).
A = h^2/(8pi^2I) = (6.63x10^34)^2/(8 x pi^2 x 4.6x10^48) = 3.8x10^21 J
You can then use this value of A to find the actual values, in joules, above.