How many Ca2+ ions are found in 2.00 mol of CaO?

Study your book until you understand what a mole is.

A mole is the molecular mass in grams. That means 6.023 x 10^23 molecules.

One mole of Ca, 6.023 x 10^23 atoms, combines with one mole of O, 6.023 x 10^23 atoms, to make one mole of CaO. Oops, O is not a molecule; the molecule is O2. So to balance the equation you have to use two moles of Ca with one mole of O2 to make two moles of CaO which has 12.046 x 10^23 molecules.

Now let's expose the trick question. There are no ions in CaO. Only molecules. Your question is like asking where they bury the survivors of a plane crash. They don't.