The amount of a substance can be converted into grams of that substance by using the molar mass. It is a physical property of a substance which describes the mass per mole of the substance. The molar mass of Ca(OH)2 is 74.093 g/mol. Dividing the given molar mass of Ca(OH)2 with given amount will yield to the moles of the substance.
165 / 74.093 = 2.23 mol Ca(OH)2