I don’t know if this question is Off-Topic or not so here I go:
When I copy the “retroarch” folder to the root of my 3DS sd card with microSD management it says I need permission to copy the “cores” folder? What do I do?
I’ve had this problem, it wasn’t the retroarch folder or anything in it but it did happen the same way. Turned out my SD card got corrupted as I checked inside the folder with GodMode9 and all it displayed was garbage. I suggest you copy everything you care about which would probably the entirety of the SD minus the "cores’ folder, Format the SD Card, then copy everything back and do a fresh install of the retroarch folder (You don’t need to reinstall the CIA’s or 3DSX’s unless there is an update to the versions of them itself). That’s how I always fix it, and I recommend you format with GodMode9 and set it to 32k clusters for faster operation, there is an option for 64kb but it’s know to make things unstable.
It didn’t have anything to do with the SD card, GodMode9 displays perfectly fine so I got help on GBAtemp and had to use FTP transfer instead! 