Since official Citra is gone, use Lime3DS or PabloMK7's Citra.

Decrypted Nintendo 3DS ROMs on the Internet Archive — Best Practices & Resources

The Internet Archive (archive.org) is a non-profit digital library. Unlike torrent sites filled with pop-ups and malware, IA offers direct HTTP downloads with a few distinct advantages for retro gamers:

A popular, smaller upload for handhelds. This collection focuses on "one-click" decrypted files without any BIOS or key requirements.

While the HShop is for real 3DS consoles, users occasionally upload bulk conversions of their .cia files to decrypted .cci for emulator users.