Well, for the New models only, they allow you to connect to your PC and indirectly manage your SD card WHILE its still in the system! Try finding a giude on this. (been ages since my New 3DS XL broke so I dunno what the official term is...)

FTPD might already be on your 3ds, it uses wifi to host the sd card, and you connect via file explorer, you can transfer files and control the sd card from there.

i forgot to update this a while back, FTPD works wonders! thanks Eskario and CDs for the help:D