Existing saves will (probably) no longer work - you'll have to export it with a save manager (like detailed in
this guide), then import after converting the game to card 2. I point out card 2 conversion because it saves directly to Gateway's SD, instead of to the Gateway's internal save chip then to the SD card on exit.
I looked back at your original post and you said your save was corrupted? The issue I pointed out results in a save not being properly saved (so whatever was there before is used). What were you doing when it got corrupted?