Train from Marseille to Paris

You can review your options on the SNCF website: https://en.oui.sncf/en/. Choose Marseille (All stations) as your origin and Paris (All Stations) as your destination. You won't be able to see April departures for quite some time, so I'd choose a date in October. The day of the week is important, so if you know what day you'll be traveling, use an October date that falls on the same day of the week.

It seems that all your possible trains arrive at Paris's Gare de Lyon.

As you can see, there are many trains that require no transfers, so this should be a comparatively easy trip. The fare you pay will depend on how early you buy your ticket and whether you buy a Ouigo ticket (which has some restrictions) or a regular ticket.If you repeat your search for a date next week, you will see demand pricing in action.

All trains leave from Marseille Saint Charles, and you should choose Paris Gare de Lyon as your destination (some cheap Ouigo trains go to Marne La Vallée, near Disneyland and 25 miles from Paris).

visit that man in Seat 61, he knows a lot about trains