??? Depends on how thick your plasticard is.
You could replace the pencil in a compass with an exacto and set it for a 40mm cirle, and just spin it around, but you leave the center hole in place.
You also might find a hole bit that is 40mm and just stick it in your drill and act like a cookie cutter, and cut out the circle.
Get something 40mm round and temp glue it to the plasticard and cut around it and file it down flush with your template, then pop the plasticard off your template item.