How much energy will be released when 10 kg of Uranium235 is completely converted into energy?

If you truly mean that the uranium is completely converted into energy, then the answer (which doesn't depend on the nature of the material) is found using Einstein's famous equation E = mc^2. Since m = 10 kg and c = 3.0 x 10^8 (to two significant figures, the precision of the mass), the energy released would be 9.0 x 10^17 Joules. Write 9, add 17 zeroes. It would more usually be written using a suitable metric prefix on the energy - 900 PJ, for example. P is the symbol for the prefix peta-, standing for a factor of 10^15.

https://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence

However, your choice of uranium-235 as the material under discussion suggests that the question is actually asking how much energy would be released through the process of fission if every atom of U-235 were to decay. This is a more complex calculation.

The fission of one atom of uranium-235 generates 202.5 MeV = 3.24 × 10^11 J, which translates to 19.54 TJ/mol, or 83.14 TJ/kg.

So 10 kg would yield 831.4 TJ (which is 0.8314 PJ, if you want to compare these two values).

https://en.wikipedia.org/wiki/Uranium-235