Actually, you do NOT need to calculate the number of moles, so you do NOT need to convert the volume and pressure. (You DO have to convert the temperature.) That's because for this problem, pV/T is constant, so the units cancel (but the temperature scale matters).
<span>200kPa * 15L / 373K = 101kPa * V / 273K </span>
<span>V = 21.7 L </span>
