We got our Arduino NANO controller from the CNC machine package that we bought. We attached it to the GRBL controller to control the movements of our CNC machine.
However, we decided not to use the CNC machine with the GRBL controller and Arduino NANO for our project. One of the reason is because Arduino NANO has too little space in its memory to support our firmware. Another reason is because the X, Y and Z axes have to be individually calibrated in addition to the extruder that has to be re-calibrated. The calibration was a relatively tedious process, hence we decided to go with Creality Ender 3 as our main chassis instead.