how many grams of BaCl2 are present in 150 g of H20 if the concentration is 0.3 m?

I will assume you intended to write 0.3m, meaning 0.3 molal since you don't seem to be able to find the caps key on your computer.

m = mols solute/kg solvent
0.3 = mols BaCl2/0.150
Solve for mols BaCl2, then
mols = grams/molar mass. You know molar mass and mols, solve for grams.