Tahoe Travel Trailer I Need Information On How To Repair A Floor Below The Slide Out In A Thor Travel Trailer?

I need information on how to repair a floor below the slide out in a Thor travel trailer? - tahoe travel trailer

No damage due to moisture in the plywood floor under the slide. I need to find a way to remove the film from reaching the ground. Some tips we are very grateful. He is a 2005 Thor Tahoe 23FB TT S