There is a direct train between Amsterdam and Paris: the high-speed train Eurostar. The reservation fees for the Eurostar are relatively high. While it may be the most convenient option, there are other alternatives to consider that can help you save money while traveling between Amsterdam and Paris with your Interrail Pass.
An IC train between Amsterdam and Bruxelles-Midi (no reservation required) and a TGV train between Bruxelles-Midi and Paris CDG Airport (this train requires reservations).
From Paris CDG to Paris Gare du Nord, you can use the RER service (which, unfortunately, is not covered by the Interrail Pass).
You can also travel using a combination of trains that do not require reservations (TER and InterCity), though that takes longer than the high-speed options.