The parish is at the ancient Notre Dame church; you can't miss it, it is in the main street of the old town, close to the bridge.
There are masses Monday to Thursday, 19 hrs. When I was there, there was a pilgrim's blessing after Mass, and I suppose it is a standard, given the number of persons beginning (or finishing, for many French) their pilgrimage in SJPP.
Anyway, an announcement with the horaires is fixed at the door.