EDIT 25/10/2013: I’ve updated this guide to now include SDXC cards, which need to be specially formatted before you try to migrate. Find the new guide here.
With demos now available on the 3DS eShop, it’s likely your original 2GB SD card will become a bit full, if it hasn’t done already. I found myself in this position today. Thankfully, I had a spare 4GB to “upgrade” to.
You can, of course, just swap your old card for your new one, but then any pictures you’ve taken and games you’ve downloaded and “extra data” and stuff won’t be on there unless you swap cards again. And we all know that swapping SD cards is the worst of all First World Problems.
Using this method, you can transfer everything from your old card onto your new card:
- Mount your old card on your computer.
- Create a folder on your computer and copy EVERYTHING from the card to it.
- While it’s doing that, put your new card in your 3DS and turn the 3DS on. It’ll initialise the card for you.
- When both these have finished, mount the new card in your computer.
- Open the folder you made on your computer, and copy everything to the root of the new card. If you’re asked to overwrite folders, or merge folders, say “yes”.
- When the copying has finished, you’re almost there. Next, on the new card, open the folder called “Nintendo 3DS”. Inside there will be folder with a huge string of letters and numbers for the name – open that.
- Inside that folder will be two folders with long random names. One of these is the folder tied to your old card, the other is the one tied to your new card. Simply copy the contents (not the folder itself) of the old one (it’ll be the one with the larger filesize) into the other one – merging and overwriting again if necessary.
- Put the new card back in your 3DS, reboot it if necessary, and you’re away!