I converted a master forge grill to natural gas and do not understand how to reset the control knob

The adjustment screws referred to in the manual are deep in the middle of the valve shaft. Remove the knobs using the hex key supplied by the grill manufacturer. Using a flashlight look down the center of the shaft. You will see a screw head, this is the adjustment screw. Turn it two turns counter clockwise with the supplied screwdriver as the manual instructs.