: Place makerom.exe and Converter.bat in a folder, then simply drag and drop your CIA file onto the .bat file to begin conversion.

—several portable tools and command-line scripts are available. These tools are generally "portable" as they do not require a formal installation process; you simply extract the folder and run the executable or batch file. Recommended Portable Conversion Tools CIA to 3DS Rom Converter (GitHub) : A lightweight, portable solution for Windows. It uses makerom.exe

: The resulting .3ds file will appear in the same directory once the "Congratulations" message displays. Important Notes

Before hunting for a converter, you must understand why conversion is necessary.