Understanding the difference between these formats is the first step in deciding if you need a converter.
If you have landed on this page, you are likely staring at a file with a .cia extension, desperately wishing it was a .3ds file. Perhaps you are a 3D modeler who received a strange asset, or more commonly, a Nintendo 3DS enthusiast who has stumbled into the confusing world of ROM formats and 3D modeling file extensions.
These are "installation packages" used by the Nintendo 3DS system. Much like an APK on Android or an MSI on Windows, a CIA file must be installed to the system’s SD card before the game can be played. Tools like FBI on 3DS are commonly used to install these files on a modded console.