Thorin reclaims Erebor, the mountain kingdom, in Peter Jackson’s The Hobbit: The Battle of the Five Armies.
Erebor is the Lonely Mountain, a vast Dwarven realm built around immense mineral wealth. The dragon Smaug seized it before the events of the trilogy, forcing Thorin Oakenshield and many other Dwarves into exile.
After Smaug leaves the mountain to attack Lake-town, Thorin enters Erebor and takes possession of the Arkenstone and the kingdom’s treasure. His determination to retain the hoard contributes to the conflict that leads to the Battle of the Five Armies.
Moria is a different Dwarven realm, located beneath the Misty Mountains. Gondor is the southern human kingdom, while Mirkwood is an Elven forest ruled by Thranduil. These locations are all important to Tolkien’s world but are not Thorin’s reclaimed kingdom.