6.022x10^23 is Avogadro’s number. Use this whenever you work with Stoichiometry involving Atoms, formula units, or molecules. 1 mol of anything is always Avogadro’s number.
Multiply everything on the top= 6.93 x 10^23
Divide by everything on the bottom = 6.93 x 10^23
Answer: 6.93 x 10^23 atoms Cu.
An atom is the smallest you can get to identify the element.
Reaction:

Magnesium is a stronger reducing agent than copper and is thus able to reduce copper(II) oxide.
Products of the reaction: Magnesium oxide and metallic copper.