Hello Edith, first of all congratulations for your trip to Paris. It is indeed the right time to come to Paris to see the most amazing Monet exhibitions ever staged. First, the
Grand Palais Monet exhibition. It is planned to be a huge success. You won't get in if you don't buy your ticket in advance. See their
website.
Marmottan will be easier to get in. Nevertheless, expect queues. You will find the famous waterlilies at
Orangerie.
Jeu de Paume is now a photography museum. Most of these venues are near
Champs Elysees. Enjoy your Paris trip.