Do I have to prepare anything before transferring?
Please make sure your Nintendo 3DS has system software version 3.0.0-5E or later. Click here for more information about system updates.
Any photographs or sound files that you’d like to keep which are saved on the target system should be copied to the SD Card prior to transfer, or they will be deleted when the target system's memory is overwritten.
Otherwise, simply connect to the Internet with both systems, and follow the instructions for performing a full system transfer between two Nintendo 3DS systems here.