The guide says use either gro0 or ux0 depending on whether you have a physical or digital of copy of P4G (since that's what the guide is for). Nothing is stopping you from using both at the same time, I do it and it's fine.
Anyway I'm glad that I could help, your save game is always found in the "savedata0:" partition because the system loads it into there regardless of what type of game you have. How the saves are structured can differ per game, but you'll always find it in that directory.
Have fun