What is Mr. Pumblechooks trade?

Mr. Pumblechook is a "cornchandler".

Mr. Wopsle, the clerk at church, was to dine with us; and Mr. Hubble the wheelwright and Mrs. Hubble; and Uncle Pumblechook (Joe’s uncle, but Mrs. Joe appropriated him), who was a well-to-do cornchandler in the nearest town, and drove his own chaise-cart.