There's no need to hijack an old thread. You can create your own.
http://www.epforums.org/showthread.p...32#post1585832
Chances are they're compressed but without knowing exactly what's going it's hard to say - are you downloading for use in an emulator or on a DS itself? You probably just need to decompress in which case use 7zip it's free.
Keep in mind the topic here is that there are no full 3DS games dumped or any working emulator for them. If just regular DS then it's ok.