After Pierre, Conseil, and Ned escaped the Nautilus, we aren't told what happened to them. I will write about what I think happened to the three men after they escaped and got back on shore.
After Pierre woke up, he found himself on the coast of Norway. Luckily, the escapees were near a town, so they managed to get enough money (by working there) for a train ride all the way to Paris, France. There, Pierre published his book, which made him rich and famous, earning him respect from the scientific community for the many discoveries he made while traveling in the Nautilus. Unfortunately, he never found out any more about Captain Nemo's story, whom he never heard of again.
Conseil continued to be Pierre's servant, not because he had to, but because he loved to be with his master and continue helping him classify animals and plants. He is not so much Pierre's servant as his assistant, though.
Ned went back to America after they got to France. He continued being a whaler, many times impressing his crewmates with stories of his times on the Nautilus, although his friends don't usually believe him and think that these are mostly tall tales conceived in an alehouse.
In conclusion, I think that the characters in the story go back to their previous jobs and tasks, but sometimes still wonder of the identity of Captain Nemo and whether their journey was a dream or not…