You can't dump game carts directly to your SD2Vita, since it takes up the game card slot, so you'd need to dump it to either the Vita memory card, or to your PC.
You'll need to pull your SD2Vita and put the game card in it's place, then make sure you have the NoNpDrm plugin installed so you can play the dumps. From there, you can dump games two main ways:
1) By mounting the gamecard via USB on VitaShell, which is the faster way. To do this, open up VitaShell with the gamecard plugged in, and choose the "Mount gro0" partition via USB. On your PC, this should pull up a disk with an app folder in it, you'll want to transfer the "gro0:/app/GAME TITLE ID" folder to your PC. Once done, you can swap back to your SD2Vita and transfer the "GAME TITLE ID" folder over via USB to ux0/app folder.
2) You can dump the games directly to the Vita memory card, but this is slower and if you don't have enough space on your memory card it might be a bit more annoying. The process is mostly the same, just instead of mounting the gamecard to your PC, you would navigate to gro0 in VitaShell, and copy that same folder mentioned above to any folder in ux0. From there, re-insert the SD2Vita, and transfer that same GAME TITLE ID folder to ux0/app folder on your SD2Vita.