Unofficially, so long as your format an SDXC card to FAT32, it will also work. The biggest anyone's ever tried is 128 GB (slightly under 1 million blocks), but 256 GB SDXC cards do exist. Of course, at this point, you're paying hundreds of dollars for an SD card. --- 3DS:4897-5935-1924; NNID: CrimsonEnigma; PSN: CrimsonEnigma (not currently in use) 'If you think a system will make you look mature, you ain't mature' -squatch
The largest size a 3DS normally supports is 32 GB, but it can support larger SD cards if those are formatted to FAT32 first. As to how to copy data from one SD card to the other, you just simply plug the first card into your computer, copy the data EXACTLY how you see it (best to copy the data into a new folder to help with this). Then remove that card, plug in the new one, and copy the data from the computer to the card. (If your computer has 2 SD card slots, then you can just copy the data directly between them) --- Stop reading my sig, you are wasting time doing so.