Help With trip to Paris, France!!!!?

So I live in the US and ive heard its better to buy metro pes here in the US. Im going to be there for a week, so which ones should I buy, I want to have access to all the sites. I also want to go to Versaille and take a tour of the Loire Valley. I am a student so I'm staying at St. Christoper's inn on 159 rue de Crim�e