UA5397 takes several routes. The most popular is between Missoula, MT (MSO-Missoula Intl.) and Chicago, IL (ORD-O'Hare Intl.), which is a direct flight. This service takes around 3 hours and 22 minutes. That said, there are likely to be other flights with the same number that are multi-stop.
UA5397 is a flight number that's used on lots of different routes. If you've booked a seat on the most common route, Missoula, MT (MSO-Missoula Intl.) to Chicago, IL (ORD-O'Hare Intl.), you're likely to be hopping aboard the Embraer 175.