Quests for Gold is a common quest type in Sea of Thieves. Players will locate Treasure Chests on islands using maps and the map table to guide them. Once the island is located, complete the task by locating the treasure (marked with an 'X" on the map), digging it up using shovels and returning it to a Gold Hoarders representative at an Outpost to be traded in for gold .
These chests can be stolen by other pirates (players) so it's a good idea to find hiding places for them on the ship.
Information on these quests past level 30 can be found Here.