There is no drive letter in Linux unlike like Window. All you can see is the label and volume. When you plug in your thumb drive the icon will appear on the desktop and your home folder. I too is a newbie and are trying to get use to it.
after googling i found a way to do it:
first: create a folder like mkdir /media/usb
then type: fdisk -l to check which device the thumbdrive is installed in
then mount the drive use: mnt /dev/sdb1 /media/usb
that's it can broswe to /media/usb