If it is a film that does nothing t have a top coat then I would not do this. Coatings need clear coat to bond to and films that have a top coat (like Xpel Ultimate Film) have an automotive grade clearcoat as a top coat on the film that can be coated.

Do you know what line of 3M film it is?

If not find out the line before moving forward.

Also you the car should be preped with a paint correction prior to installing the film for the best results
Its the 3m pro series self healing film. I have emailed 3m directly and will see if they respond.
Thanks!