To change mass to moles of sodium, you need to use the molar mass of sodium. The molar mass of sodium is 22.99 grams per mole. This means that for every 22.99 grams of sodium, there is 1 mole of sodium atoms.

1 mole of Na = 22.99 g of Na

Moles = mass(g) / Molar Mass(g/mol)