To answer this question, you need to change the sodium phosphate unit into mol and doing the reaction. Sodium phosphate or Na3PO4 molecular weight is 163.94 or 164 rounded up. Then the amount should be: 492g/ (164g/mol)= 3 mol
For every 1 mol of Na3PO4 there are 4 mol of oxygen element. To made 1 mol of O2 molecule, you will need 2 mol oxygen element. Then the amount of oxygen should be: 4/2 * 3 mol= 6 mol * 6.02 * 10^23= 36.12 * 10*23= 3.61 * 10^24
