What mass of helium is needed

Okay so, Ideal gas law PV=nRT
I'm given V=200L; P=135atm; and T=297K (and R is .08206L/K atm/mol)

I need to find out what mass of helium is needed.

I keep working it out and getting 1107.84moles, but I'm not sure where to go from there to get mass.

PLEASE HELP! 5 stars!

Using your figure of 1107.84 moles and the Mol.mass of Helium is 4.0g/mol.
This means that 1.0 mole has a mass of 4 grams. So, 1107.84moles x 4.0 g/mole = 4,431.4g.