The equivalence factor I should use should involve the Avogadro Number which is 6.02 * 10²³.
6.02 * 10²³ molecules of Oxygen are present in 1 mole of Oxygen molecule.
4.28 * 10¹⁹ molecules of Oxygen would be:
= 4.28 * 10¹⁹ * 1 /(6.02 * 10²³)
≈ 0.0000711 moles
So 4.28 * 10¹⁹ molecules of Oxygen is ≈ 0.0000711 moles