LATE 2012 mac mini USB 2.0 not 3.0

I just recently purchased a used late 2012 Mac Mini. It should be an upgrade over my 2010 model. However, I think I have a real oddball here. Everything I've read claims that this should have 4 USB 3.0 ports. My system report shows mine as USB 2.0. I thought perhaps I received a 2011 model instead of the advertised 2012, but when I pull up System Information, it shows "Macmini6,1" (not 5,2, which is the 2011 model). I plugged the serial number into EveryMac's Serial Number look-up program and it shows "Late 2012." The EMC number is 2570, which is the "Late 2012." Any ideas out there? Thanking you in advance.