If it is three moles of NaOH i.e 3 NaOH
The number of atoms in each mole = 3 moles atoms
so total moles of atom = 9 moles of atom
in each mole of atoms = 6.023 X 10^23 atoms
so total atoms in three moles of NaOH = 9 X 6.023 X 10^23 atoms
= 5.4207 X 10^24 atoms