It sounds like your pen drive is not mounted. These devices look like an exernal hard drive to linux.
Some things to try. Open a terminal, and run the command 'lsusb' ( without the quotes ). You should get a listing of attached USB devices. The pen drive should be listed. Here is what it will look like.
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 002 Device 002: ID 0461:4d03 Primax Electronics, Ltd Kensington Mouse-in-a-box
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 004: ID 0781:5530 SanDisk Corp.
Bus 001 Device 003: ID 5986:0182 Acer, Inc
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
The SanDisk is my pen drive. If it does not show up, then you may have a driver problem. If it shows up, try to mount it.
This takes root user. You need a directory to mount it to. Most distros give you an empty directory called /media for this purpose. The command would be;
'sudo mount /dev/sr0 /media/sr0' ( no quotes ). sr0 is the device, this gets created when you hot plug the stick. It may be a different device on your system. To find out, go to the /dev dir. Type 'sr' and press tab, twice. That will list all occurrences of sr. Success is indicated by no response from the system. Do a cd /media and then a ls command. You should see the files on the stick.
You don't need any special programs for USB sticks. Any file manager will work.
Hope this helps.