Molarity = moles of the species of interest/liters of solution.
We know the liters of solution are 50. ml x 1 L/1000 ml = 0.050 liters.
So now we need to find moles of FeCl2 and then moles of Cl- ions (the anions)
Molar mass of FeCl2 = 126.8 g/mole
moles FeCl2 present = 0.10 g x 1 mol/126.8 g = 7.89x10-4 moles
moles Cl- = 7.89x10-4 moles FeCl2 x 2 moles Cl- / mole FeCl2 = 1.58x10-3 moles
Molarity of Cl- = 1.58x10-3 moles Cl- / 0.050 L = 0.0316 M Cl- = 0.32 M Cl- (to 2 significant figures)