Mr. Mine Wiki

Large Cargo is the level 6 Cargo Bay upgrade for the Drill available to be found in one of the Treasure chests.

It also can also be bought from the Golem for $20,000,000.

It requires 50,000 Diamonds. Cargo Bays does not add any wattage to your Drill, but they do expand your capacity. 

Its capacity is 500,000 units