Do iPod Nanos have USB 2 or 3?
All iPhones and iPods with the Lightning connector use USB 2.0. From Wikipedia:


  The Lightning connector … provides an interface to USB 2.0 (for data and charging)


Also, if you look the USB end of a Lightning cable, it doesn't have the additional pins for USB 3.0.

There is actually no point to having USB 3.0, since the flash memory in iPods and iPhones is not fast enough to benefit from its speed.