First off, the equation's not balanced. You ALWAYS ALWAYS have to check the equation.

XeF_{4} + 2H_{2} → Xe + 4HF

Then if we assume that everything in the equation is an ideal gas, then we can simply conclude that for every 1 cm^{3} of Xe produced, there will be 4 cm^{3} of HF produced, but that doesn't answer your question of the number of moles. However, it does tell you that you have 200 cm^{3} of HF

I would do the calculations this way:

Volume of Xe Produced = 50.0 cm^{3}

Amount of Xe Produced = (50.0/1000)/24.5 = 0.002041 mol

Amount of HF Produced = 4*(0.002041) = 0.008163 mol