Emulation I need help with Flycast or Retroarch emulating Dreamcast

[PalmeraJam]

I've been trying to introduce Shenmue into Retroarch or Flycast for several days, but I can't get Retroarch or Flycast to show the DC roms... I don't know in what format or where to add them exactly... maybe I have the SD paths wrong... I have DC cores in the Retroarch cores folder and I have put the games in .7z and .gdi format, but I am unable to see them or Retroarch shows the DC category.
My Retroarch version is the 1.14

I have tried looking for guides and I have used the forum search bar, but I have not had any luck, please, if someone could help me in any way..