Bus from Vakkotavare to Gällivare

Hello! My friend and I are planning a trip this summer and we are considering getting off the route at Vakkotavare. I know there is a bus route to Gällivare, from where we’d take the night train to Stockholm, however I can’t seem to find a way to book the bus. Does anyone have any experience with it? Do we even need to book the bus or can we just get on with no worry about it being full? We‘re planning to go during peak season, so the bus should run twice a day and were planning on taking the afternoon one.