Where ican get the stone plate in explorers of time?

In "Pokémon Mystery Dungeon: Explorers of Time," you can obtain the Stone Plate by defeating the boss Pokémon Regirock, which is located in the dungeon called the "Cavern of the Ancients." Additionally, you can find it as a potential reward in treasure boxes or by defeating certain wild Pokémon in dungeons. Make sure to explore thoroughly and check your treasure box after completing missions for a chance to receive it.