If the waste you have contains 100.0 grams of silver nitrate, how many mols of silver nitrate is this

The number of moles is simply calculated by taking the ratio of mass over the molar mass. The molar mass of silver nitrate AgNO3 is 169.87 g/mol. Therefore:

number of moles AgNO3 = 100 g / (169.87 g/mol)

number of moles AgNO3 = 0.59 moles