AVR programmer necessary?
The ATmega168PB does not feature an USB interface. What you have there is either


an evaluation board with a built-in ISP programmer


or


a board with a USB-RS232 converter and a pre-flashed bootloader on the µC which employs self-programming of the other parts of the on-chip flash ROM through the RS232 pins.


You cannot flash an ATmega168 coming fresh from factory without an external programmer.

I strongly recommend to buy or build an ISP programmer. You will need it from some point on.