Use cd to change directory. Namely cd /mnt/uba1
It needs to be mounted writable first of course, for this you can use the desktop icon.
If it's mounted read only (check by typing mount) you can change to readwrite with sudo mount -o remount,rw /dev/uba1 /mnt/uba1

May I suggest some reading:
http://homepage.powerup.com.au/~squa...inuxmanual.pdf (don't know why it's called one page manual since it's two pages unless you print double sided )
http://www.tuxfiles.org/linuxhelp/