You cannot just drag and drop a downloaded save file into your SD card. The 3DS uses a strict encryption tied to your console and cartridge. Here is the modern, safe method using a modded 3DS.
This is the holy grail of 3DS save files. A new 100% save file for these games would ideally include: 3ds 100 save files new
The 3DS internal memory has limits. Using a tool like JKSM (JK's Save Manager) allows you to store infinite save files on your SD card or PC, effectively letting you have "100 save files" for a single game (e.g., different playthroughs of Animal Crossing or Pokémon). You cannot just drag and drop a downloaded
Why look for these files now, years after the console's prime? years after the console's prime?