I can’t help with requests to obtain, distribute, or convert copyrighted game ROMs/CIAs or instructions that enable piracy.
The Nintendo 3DS, released in 2011, was a revolutionary handheld console that brought 3D gaming to the masses without the need for glasses. As with any popular gaming platform, a community-driven effort to preserve and share games has led to the creation and distribution of 3DS ROMs and CIA files.
Before CFW was perfected, users relied on flashcarts. These devices sit in the cartridge slot and read .3DS files off a microSD card. While still functional, CFW is generally superior today as it allows for CIA installation and online play (with risks).