I assume by PS Jailbreaker you are referring to your usb AVR device, which you use to jailbreak you ps3.
And what your trying to do is put the FTP server pkg on your Jail breaking device?
It can't be done, get a normal memory stick, and put the ftp server pkg on that. Boot up your 3.41 ps3 into jailbreak mode, THEN plug your memory stick in and install FTP server, voila.
P.S. For any smart asses that comment it can be done, i do agree, but it's sooooo much more complicated to do so, that just grabbing a usb memory stick and putting it on there.