If you're wondering why the SNAP-PACs do NOT have the ability to format your microSD card there remotely for you, it's because the SD Card association does not recommend using OS utilities to format microSD cards. Instead use the one they provide, see this link: https://www.sdcard.org/downloads/formatter_3/
The question I want to ask you is, why do you need to format that card? Do you know how those files got corrupted? Have you tried other ftp tools (like even the DOS command-line ftp option) that might let you delete the files you don't want? I like FileZilla too. Just curious.