There are several methods to dumping DS games. With the DS, your options are rather limited
1: Dump using a Slot2 cart like EZ-Flash VI. This requires either slot1 to boot into DS-Mode or FlashME
2: Wifi dump, which is PAINFULLY SLOW. Requires a flashcart.
With the 3DS, you can use a hacked 3DS and dump games using GodMode9