So I just got another SD Card (an 8 gig) and I want to transfer all of my 3DS games and apps from my original SD Card to the new one, I've tried copy and pasting it using my computer but it dosen't work, what do I do? I also don't want to lose all my progress and save data on Swapnote and Ambassador games.
Here is the safest (and hopefully quickest) way to get stuff transfered without losing any data:
Install the program on your computer. After doing so, insert your brand new SD card into the SD Card slot and run the SD Card Formatter.
Now onto the SD Card on the 3DS:
Basically the gist of formatting the card is:
While the former is not really required with regards to data transfer, it obviously helps in case you do run into problems like errors, or you just came from buying a brand spankin' new SD Card only to find it "wont work".