How do I find the molar mass of - lead(II) chloride?

First you need to figure out the formula of the material, PbCl2. The atomic weight of lead, Pb, is 207.2. The atomic weight of chlorine, Cl, is 35.4527. You add the atomic weight of lead to double the atomic weight of chlorine (there are two chlorine atoms in a molecule): 207.2 + 35.4527 + 35.4527 = 278.1054. That is the atomic mass of one mole of PbCl2. Usually, it's expressed in "gram moles" or 278.1054 grams.