Paris to Lourdes

This may help

https://www.rome2rio.com/s/Paris/Lourdes

Eugene,
I made the trip four years ago via TGV direct from Montparnasse to Lourdes. Zero transfers, and the train only makes stops starting at Bordeaux/Pau/Dax etc. I just looked at the Bahn website and it looks like they’ve shaved a little time off the train trip, but it still takes the majority of the day. I was in 2nd class so I bought a sandwich before I got on the train and a cup of coffee while onboard. If you don’t mind spending 6 hours on the train, it’s a pleasant journey, and it’s cool to see the landscape change, particularly once in the Pyrenean foothills. When in Lourdes, I highly recommend the Château Fort/Pyrenees museum in addition to the religious sites.