From Trieste to Pula, there is a travel distance of about 120 km. Trough out the year there are several daily departures between the cities, in the summer season additional seasonal buses are running. Driving time for by bus is about 2.5 to 3 hours.
In Trieste the bus drive from Piazza della Libertà / Via Flavio Gioia 2, which is in the centre of town, just next to the train station? In Pula the buses stop at the main bus station which is about 800 meter from the Pula Arena.
You can see timetable for buses from Trieste to Pula below, and if your are travelling from Pula to Trieste you can see the timetable here