OK, your Scanner should show up under Firewire, not USB. It is a Firewire scanner; if that isn't the case, well...???
I've attached a zip of the inf file. After you download the file make sure you do this...
1- Save the file (inf) to a location (folder) of
your choosing...
Example: I created a
folder called "
Nikon Files" and placed it inside inside the "
NKScan4" folder located at
C:\Program Files (x86)\Nikon\NkScan4 - Thus the folder now looks like this...
C:\Program Files (x86)\Nikon\NkScan4\Nikon Files 2- "After" you install the Nikon Scan software go to
C:\Program Files (x86)\Common Files\Nikon\Driver\Scan1394 and copy this file "
NKScnUSD.dll" to the same folder (Nikon Files) that the inf file is in.
The
Nikon Files folder should now contain these two files...
NKScnUSD.dll and the
Scanners.inf 
C:\Program Files (x86)\Nikon\NkScan4\Nikon Files
After that....
6- Go to Device Manager – Control Panel, Device Manager and look for the "Unknown Device" (
your scanner) with the yellow triangle.
7- Right click on it and choose "Update
Driver Software" and choose "Browse my computer for
driver software"
8- Click "Browse" and find the folder/location where you put your created inf file, EX:
C:\Program Files (x86)\Nikon\NkScan4\Nikon Files and click "Next" this will install the inf driver for the scanner.
9- That’s it – Your Nikon Scan software should now be fully functional.
Once that's done your device manager should look something like this...
Let me know if this worked.