NOTE - Please feel free to correct the title if it is not describing correctly what I am asking here.

What I want to know is, how can I know via Nautilus or a GUI app, the filesystem direction of a pen drive or external usb drive. For example, when I connect a external hard drive called "Mary". In Nautilus or looking at the properties of the device in Nautilus it mentions that is was mounted in /media/mary but I want to know if it is /dev/sdb1, /dev/sdc1, etc...