Using Fusion
In Fusion 360 open your circuit board.
Click on Manufacturing at the top.
Choose CAM Processor.
Use the minus sign at the bottom of the Output Files list to remove unwanted files. Since I used the mirror ULP the copper trace pattern I want is Top Copper.
Click on Process Job.
Select or make a folder somewhere easy to find.
Inside a set of folders you should find a gerber file, eg. copper_top.gbr. We will use Flatcam to turn the gerber file into G code.