If you are at a console (no X, no GUI env), then it will not automount. You will need to mount it manually. The GEOM_LABEL output is telling you that there is a /dev/msdosfs/USB DISK device created for it.
If you are in a GUI env (GNOME, KDE, Xfce, etc), then it may automount, depending on the configuration. If it does automount, it will most likely appear as /media/msdosfs/USB DISK.