How many moles of oxygen must be placed
in a 3.00 L container to exert a pressure of 2.00 atm at 25.0°C?

I did (2.00)(3.00) divded by (0.0821) (298) and I'm still getting the answer as 27,700 or something like that. I know I did the equation right? But, I keep getting the wrong answer. Help please.