You don't show the molar mass or the compound so we don't know how many grams. Do what GK suggested to find the moles, then multiply by the molar mass.
For the Cu2O part of the problem, the secret tip is to write a balanced equation.
2Cu2O ==> 2Cu + O2
The equation TELLS you that 2 mols CuO will produce 1 mol O2.
You can do this by ratio/proportion or you can use the dimensional way of doing it. The dimensional way is to start with what you have (2.3 mols Oxygen is what you want) and convert that to moles Cu2O.
2.3 mols O2 x (2 mols Cu2O/1 mol O2) = ?? Notice how the units cancel. We don't want moles O2 (and they cancel) and we want the answer to be in mols Cu2O and that unit does not cancel.