Doraemon Movie 08: Nobita and the Knights on Dinosaurs

Doraemon builds an underground hideout for his friends, but Suneo gets separated from the group. When they return to the entrance, they find it's been blocked, forcing them to search for an alternative route. Their new path leads them to a strange world filled with dinosaurs, where they're rescued by Vanho, a soldier from a nearby kingdom. Vanho claims to have found Suneo, and upon being reunited, they learn about the kingdom's intentions to study Doraemon's group as specimens for their own purposes.