Dumping game cartridges is done the same way like dumping savegames.
EZFlash 3in1 method
The only difference here is that you might have to swap the cartridges more often since the Flash memory of the EZFlash 3in1 is only 32 MiB and some games are up to 128 MiB in size.
There’s a nice tutorial with pictures at monroeworld.com.
Here are some estimated times for dumping different sized game cartridges (copied from that page):
| Game size | Number of passes | est. time needed |
|---|---|---|
| 4 MiB | 1 pass | 2min 30sec |
| 8 MiB | 1 pass | 3min 15sec |
| 16 MiB | 1 pass | 4min 45sec |
| 32 MiB | 1 pass | 9min 30sec |
| 64 MiB | 2 passes | 14min 15sec |
| 128 MiB | 4 passes | 19min 00sec |
| 256 MiB | 8 passes | 38min 00sec |
Wi-Fi method
Be warned that the Wi-Fi transfer speed is somewhat “limited”. Dumping a 128 MiB game takes almost 2 hours. So make sure your NDS is connected to its power adaptor.
ROM Trimming
Game cartridges have the typical memory ICs in binary sizes (8, 16, 32, 64, 128, 256 MiB) although the game often doesn’t occupy the whole memory. That means if a game is 35 MiB in size, it is shipped on a 64 MiB cartridge. When dumping, you’ll dump the whole 64 MiB although the last 29 MiB are empty (filled with 0x00). So you can save a lot of space if you trim a ROM down to the real size.
Games which use the WiFi feature mostly store their connection info in this empty space so using the wrong program to trim a ROM will break online capability of games.
A good trimmer is NDSTokyoTrim which can detect WiFi-games and leaves the space for their settings.