From what I used to know, the dreamcast used GD-ROM?
a non-standard disc size but you could back-up the discs to CD-rom using your dreamcast & a serial cable connected to the PC and one of the emulators made the connection.
Then you could burn it to CD & play it on the dreamcast.
If it took up the whole dreamcast disc you had to use a boot disc to run the game first because those files had to be moved off in order to fit the game.