Hi Jill, what a great trip to look forward to!
To get from Amsterdam to Bruges, you need to change trains in Antwerp/Antwerpen. For Brugge to Paris, you’ll need to change at Brussels Midi (also called Brussels South or Brussel Zuid)
The Antwerp - Bruges and the Bruges - Brussels part is easy. These trains have free seating and can’t sell out, just like a train on the NY Subway can’t sell out. Tickets aren’t tied to a specific train, you can take any train on the day mentioned on your ticket.
Amsterdam - Antwerp and Brussels - Paris is a different matter.
Amsterdam to Antwerp can be done on 2 different trains;
1) The highspeed train Thalys. This train runs from Amsterdam to Paris with stops in Belgium in Antwerp and Brussels. Tickets are train specific and you need to book a seat. These tickets can and do sell out, especially on popular times, such as early in the day. These trains use airline style pricing, with last minute tickets usually costing more.
2) The regular IC train. Tickets for this train can’t sell out. There is free seating, just like in the Belgian domestic trains.
Brussels to Paris can only be done on the above mentioned Thalys train.
Even though you need to change trains, you don’t need seperate tickets. You can buy 1 ticket to cover your entire journey from Amsterdam to Brugge and 1 ticket to get from Brussels to Paris.
Since both your journeys involve trains in Belgium you can buy your tickets here on the website of the Belgian national railway company https://www.b-europe.com/
