These are the results. The first listing lists only two files while
the second lists all files.

edbarx@edbarx-pc3:~$ find /lib/udev/rules.d/ -name '*usb*'
/lib/udev/rules.d/39-usbmuxd.rules
/lib/udev/rules.d/73-usb-net-by-mac.rules

edbarx@edbarx-pc3:~$ find /lib/udev/hwdb.d/ -name '*usb*'
/lib/udev/hwdb.d/20-usb-classes.hwdb
/lib/udev/hwdb.d/20-usb-vendor-model.hwdb

Plugging in a USB thumbdrive, a new device name sdb1 was listed
automatically under /dev. Using this with mount as root I could browse
the contents of the USB thumbdrive in a terminal using cd and ls.

I also cannot mount camera memory cards. Maybe this issue is due to
the fact that the hardware was not recognised by the kernel.