How many moles are in 3.01 x10^22 atoms of magnesium?

Avagadros number states that 1 mol of any substance is made of 6.022 x 10²³ units.

In this case 1 mol of Mg is made of 6.022 x 10²³ atoms of Mg.

Therefore if 6.022 x 10²³ atoms of Mg make up - 1 mol of Mg

then 3.01 x 10²² atoms of Mg made of - 1 / (6.022 x 10²³) x 3.01 x 10²²

Number of Mg moles - 0.05 mol of Mg