Most of the time this concept is clear if you simply spell USB.
As a completely made up, fictitious example, suppose I were to lose my USB
drive.
I might sign to my wife: YOU SEE MY USB RECENTLY?
She would then instantly know I'm asking if she knows the location of my
"USB drive."
However, suppose you are talking about various types of wires and cables.
If you spelled "USB" during that conversation it would refer to the a "USB
wire" not a "USB drive." Thus the interpreted meaning depends on
context.
Now, if you really and truly needed to indicate specifically a USB Drive,
(the kind you plug into a computer), then you would spell USB and use a
"Classifier: G" or a "closed X" to mime the process of plugging a USB drive
into a computer.
USB Drive:
Spell USB, then mime plugging in a USB drive.
You can use either a "G" handshape like below, or a "Closed X" handshape
like above as you mime the process of sticking a USB drive into a port on
your computer.
