try to download a "4.5TB Everything Pack" as a beginner. You will spend weeks verifying the files, and half of them will be Japanese dating sims and demo kiosks you will never touch.
: "Raw" ROMs often contain junk data to fill the physical capacity of the cartridge. Decrypting these files removes this padding, significantly reducing the file size. 3ds Complete Rom Set Size
Because the 3DS scene is mature, most sets have been verified with or 3dsconv . Always download from sources that provide SHA-1 hash files. A "complete" set with corrupted ROMs is worthless. try to download a "4