Under those conditions for temperature and pressure, 0.3 moles of methane would occupy that volume.
You have all the information you need to solve for the number of moles of methane that would occupy 4.3 L at a temperature of 400 K and a pressure of 2 atm.
Your tool of choice will be the ideal gas law equation
Plug your values into the equation and solve for
Rounded to one sig fig, the number of sig figs you gave for the temperature of the gas, the answer will be