If you're asking about DMC3:
1. While playing press start
2. Go down to file
3. Go down to devil arms
From there, choose whatever weapon you're fighting with or want to fight with and it will tell you what combos are available to you while using that weapon. Some combos you have to buy, and of course most of the devil arms you have to obtain.
If you want to know attacks with certain styles, just select stlye in the file menu.
As for DMC1 and DMC2, I have no idea at the moment. Sorry I can't be of help to you if one of those was the game you were asking about.