Need help to make arrangements for travelling from Aix to Lourdes using public transportation. Can you go by bus or train? and how do we do it?
Rome2Rio.com is a good tool for beginning to explore your options. I day "beginning" because the details it displays (fares, travel times, frequencies) are utterly unreliable. However, it's usually accurate about the existence of trains or buses, where you might need to transfer, and the companies offering service. If you keep clicking through, you'll usually arrive at a link that takes you to the correct company's website, where you can find the schedule and fare. Be very careful about dates, because day of week and holidays can make a major difference.
This will be a long trip. Assuming Rome2Rio can be trusted, there will be a train change in Toulouse, which is a very nice pink-brick university city. Consider spending a night or two there.
I haven't gone to the schedule websites to verify, but Rome2Rio is suggesting a bus between Aix and Marseille even though there is definitely train service. I guess the bus is substantially faster. You may decide it's not worth the hassle of switching transportation modes, especially since Marseille St. Charles train station is set at the top of a most impressive set of stairs. (You can walk clockwise part of the way around the building to find an upward-sloping street instead, then you'll be able to locate an escalator to take you the rest of the way up.)