SD card - Wikipedia
For Nintendo 3DS, Nintendo 3DS XL, and Nintendo 2DS, the game card slot is located on the back of the system.
Cards Tier List and Guide - The Tower - Idle Tower Defense Wiki ...
For Nintendo 3DS XL and Nintendo 2DS, the SD card slot is located on the right side of the system.
Next, how big is the SD card you're using in the source ...
If you're low on space, you can replace the SD Card that came with your 2DS, 3DS, 3DS XL, New 3DS or New 3DS XL with another.