You cannot currently view your departure or arrival terminals in the Hopper app. The best way to find this information is to either contact the airline directly or manage your booking on their website.
Terminals are often not determined until 24-hours from your departure date and are also subject to change within that period and the moment you receive your boarding pass. If you're going to contact the airline to request the terminal information, it's best to do this within one week of departure.
The departure gate will usually not be determined until you get to the airport, and you will often need to check the airport screens during layovers to find out your boarding gate.
Good to know
Airlines can make changes to the departure or arrival terminal or gate at any time. It's always best to check the departure and arrival screens at the airport when travelling to have the most current information.