I'm travelling from Amsterdam to Paris with Thalys. I have limited time to get from Gare du Nord station to my hotel in 15th arr. What is the quickest way to get to the Metro at Gare du Nord in order to catch the train to the Dupleix Metro station?
The quickest route would not be Metro alone, but RER B towards Robinson, transfer at Denfert-Rochereau to Metro 6 direction Charles de Gaulle-Etoile (Arc de Triomphe) until Dupleix station.
Upon arrival there will be plenty of signage for RER or RER B trains. You'll want to follow those to the lower levels for RER platforms.
Gare du Nord photos to help you get oriented a bit.