Decrypting or extracting content from CIA files is generally for legally owned, personal backups or homebrew — sharing or converting commercial game assets without permission may violate copyright laws.
The most reliable tools for this conversion are listed below: Recommended Conversion Tools
There is no single, one-click "CIA to 3DS converter" link that works the way you imagine. But that doesn't mean the conversion is impossible. In this 2,000+ word deep dive, we will explain why the links are broken, the exact method to perform the conversion yourself, and where to find the legitimate tools (not a scam link) to get the job done.
Happy converting, and stay safe in the homebrew community.