From GameBrew - a wiki dedicated to Video Game Homebrew.
Wooddumper 3DS is a homebrew application that allows you to dump NDS games to the 3DS SD card. It is written based on wooddumper slot2 r89 by swapping out the arm7 binary and changing the dump path.
This was later ported to HiyaCFW as wooddumper4hiya by ahezard for DSi.
Available in CIA format.
Copy .cia to your SD card and install it with the CIA manager of your choice.
WoodDumper r89 now usable as DSiWare on 3DS (ApacheThunder)