Turn off your 3DS. Hold the Start button and press the Power button to boot into the GodMode9 tool.
Downloading ROMs from any third-party source carries inherent risks, but following these guidelines will keep you safe: where to find decrypted 3ds roms
Watch these guides to learn how to decrypt your 3DS files for use with emulators: How to decrypt 3DS ROMs to make them work on Azahar Retro Wolf 13 Turn off your 3DS
Subreddits like r/Roms maintain a centralized, pinned "Megathread." This megathread contains direct links to external, cloud-hosted storage drives (like Myrient or Google Drive mirrors) that feature complete libraries of decrypted 3DS games. where to find decrypted 3ds roms