You can either solder the wires directly to your 3DS > SD adapter (You open the SD adapter and solder the wires to the contacts that a mSD would normally use) > Close it back up > Insert into the Anker.
You could also solder wires from the 3DS to a female jack > Solder wires from a male jack to SD adapter > Same as above.
https://gbatemp.net/threads/3ds-hardmod.372859/#post-5129148
Edit: The second option (non temporary one) is the better choice imo. That way you will always have the hardmod incase you screw something up again.