So the tab doesnt recognize the flash drive? Are you running honeycomb 3.2? If not then you have to try to format the flash drive to fat32 in order for the tab to pick up the drive since the tab running anything below 3.2 cannot recognize ntfs drive format (unless you rooted the tab and installed the drive mount app)
What file manager are you using?
I use es file manager. When you open this one I believe its set to default open for internal storage. So long press the blue star in the upper left a new list of folders will appear. Choose mnt, this folder contains all the storage options (internal, external, usb etc) if its not listed here the tab isn't recognizing it. You can try restarting the tab with the drive plugged in and see if that helps.