I'm a bit confused by your mention of a USB connection, but perhaps I'm still thinking in terms of several years ago when I bought a Flash Path (Floppy)card reader.
If we are talking about the same sort of device, then the thing that looks like a floppy has a slot/slots in it to take the card.
Even with XP you still need the supplied software to make the system recognise the "floppy" as a car reader, but there is no need to open the box. The existing floppy drive accepts it.
If I am way off the beam, I apologise