Well, first of all, mouse dropping are very small, only about 3/8-inch long (or less) and thin. So if you have a large pile of Poop this would indicate there being a larger animal gaining entry to your RV.
The Mice? It's not uncommon for them to tear up paper products, and getting into food items stored in cardboard boxes.
Your first thing to do is to clean up all of their mess, and then searching for the points of entry they are using and sealing these places off. Then, you can tell if there are more coming into your RV, by any new droppings or damage.
As long as wild animals can get into your RV and have a source of heat or protection from the cold winds, they will take up residence in our RV, so you must get rid of any points of entry.