Downloading a full ROM set for games you do not own is illegal copyright infringement. Nintendo is notoriously litigious regarding their intellectual property. They view ROMs, even those of decades-old games, as a threat to their current business model (which includes selling remasters and Nintendo Switch Online subscriptions).
You need a modded "New 3DS" or original 3DS with Luma3DS custom firmware. Follow the definitive guide: 3ds.hacks.guide (Do not use YouTube videos—they are outdated).
Downloading a full ROM set for games you do not own is illegal copyright infringement. Nintendo is notoriously litigious regarding their intellectual property. They view ROMs, even those of decades-old games, as a threat to their current business model (which includes selling remasters and Nintendo Switch Online subscriptions).
You need a modded "New 3DS" or original 3DS with Luma3DS custom firmware. Follow the definitive guide: 3ds.hacks.guide (Do not use YouTube videos—they are outdated). nintendo 3ds full rom set