Can a ps3 memory card adaptor be used to save games on?

I downloaded legacy of kain soul reaver a few months ago, but it says it isn't compatible with the internal memory card on my ps3, so i can't save on it. i was thinking about buying a memory card adaptor, but i don't want to waste money if it can't save games. if it can be used to save games on, how do i save on it?