If I filed a motion to dismiss in a civil lawsuit and the court has not ruled on it within 120 days, what form do I file with the court to have the case dismissed?

If your filed motion to dismiss a civil lawsuit has been taken under submission for more than 120 days but there has been no ruling upon it, there are no forms for you to file. You simply have to wait it out. For you to file some motion to compel the judge to make a decision sooner than the judge is ready to do so in my opinion will do more harm than good.

I suggest that you simply wait out the process.