I am interested in the Pompei Museum. We have been to the excavation site and are returning next year. We would like to see the museum as well this time. Is it at the same location as the excavation site? What are the hours of operation and the entrance fees? How long is the average time to your?
Do You mean the MANN in Naples near the Museo Metro stop?
If the OP is not referring to the Archeological Museum, which is in Naples, then it must the the Boscoreale Antiquarian Museum which is in Pompeii. It looks like you need an online advance purchase ticket, unless you want the 3 day combo ticket.
http://pompeiisites.org/en/visiting-info/timetables-and-tickets/