New Lenny Conundrum

Lenny Conundrum
Q:In the Virtupets Space Station, there are two water tanks providing water to the station: a primary water tank, which is a sphere with a 4.5 metre radius, and a much larger backup water tank. During the busy Space Station tourist season, the primary water tank became empty. Dr. Sloth ordered his Grundos to carry bucketfuls of water from the larger backup water tank to the primary water tank.
Dr. Sloth ordered his Grundos to fill the tank so that the water is exactly 6.5 metres deep at the center. If one bucket of water holds exactly 10 litres, how many bucketfuls of water are required to fill the tank to the required depth? Round up to the nearest whole number