To get the "Where I Belong" trophy, you need to stand on the highest mountain in the game, which is found at the following location in the "Qachas" region. Due to its height, it is easy to spot. However, during the story you instantly get hit by lightning when getting near this area, and it can easily kill you. After the story, the lightning will stop and you can reach the mountain top safely. You can fly there with any helicopter or plane, which you unlock as airdrop requests automatically from securing new regions.