First you need the molecular formula for copper (I) chloride. Since it's copper (I), the charge on copper is +1. Since Cl is in Group 7A (or 17, depending on your periodic table), its charge is -1. The empirical formula is CuCl, because since they both have a charge of +/- 1, only one of each is needed to cancel out. After a quick google search, the molecular formula is also CuCl.
The molecular mass of CuCl is 99 g/mole (63.55 + 35.45).
Like, ARGOS++ said, the ratio of Cu to CuCl is 1:1.
Now you just need to find the moles of CuCl (grams of CuCl divided by the molar mass), and then multiply that by Avagadro's number.