I will arrive in Paris on Wednesday until Monday. There is a cart for 3 or 4 days, using metro ,RER and train?
For Wednesday to Sunday the best pass card to use is Navigo Decouverte week pass. Then for Monday, if you only need a single ride, use a single-use RER ticket. If you need multiple rides, you can add a Navigo Day pass onto your Navigo Decouverte for Monday.