The correct answer is Levi.
During the organization of Israel for their march from Sinai, the tribe of Levi was set apart to attend, guard and transport everything pertaining to the Tabernacle from camp to camp.
This required that these sons of Levi, and their families, the Gershonites (7,500 men); the Kohathites, (8,600 men) and the Merarites, (6,200 men) be located around and close to the Tabernacle.