For Atmel studio 6.1 or later. Please see here :
Download from gallery : https://gallery.atmel.com/Products/Details/6873be43-0628-46ac-ba83-286869a3d97a
The Atmel USB driver can be downloaded manually from here. All Atmel studio installations carry the USB driver along with them, but the latest would always have the updated drivers for Atmel AVR / AVR32 /SAM tools and debuggers. I guess the Atmel USB driver is backward compatible, meaning that the latest could be used for any versions of Atmel Studio or Avr Studio 5.0 or later. J
Have a good time with studio.