Sandify. Use the “SCARA Gcode” export format. That format outputs X and Y, but those represent angles for the shoulder and elbow joints. Your use case is exactly what it was written for. Once you have a machine you can move around, you can work out the details.
Universal gcode sender should be a good first step with grbl. There are many options.
No conversion is really possible. You can save the file from sandify and open it back up later. Or you can also export as .thr and import it as a layer. Sanidfy won’t properly import scara gcode.