Download the latest version of "3DS Simple CIA Converter" from a reputable homebrew repository (like GBAtemp). Extract the ZIP to a folder on your desktop (e.g., C:\3DS_Converter ).
: Place the .3ds file in the /gm9/in folder on the SD card. .3ds to .cia converter
From Cartridges to Console: The Evolution of 3DS File Formats Download the latest version of "3DS Simple CIA
This is the most reliable method as it uses the console's internal keys to handle encryption. 3DS Hacks Guide Copy the file : Place your file anywhere on your 3DS SD card. Launch GodMode9 : Hold the button while powering on your 3DS. Locate the file : Navigate to [0:] SDCARD and find your on the file. From Cartridges to Console: The Evolution of 3DS
For advanced users scripting the process.
(Exact commands depend on the chosen toolchain.)