Which equivalence factor set should you use to convert 2.68 x 1011 atoms of silver (Ag) to grams of silver?

The relative Atomic Mass of silver is 107.868, so 107.868 grams of it is equivalent to one mole or approx 6.0221409*10^23 atoms.

So the equation is

Grams of silver = (2.68*10^11/6.0221409*10^23)*107.868