21 Then the Kohathites set out, carrying the holy things. The tabernacle was to be set up before they arrived.

Read Numbers 10:21 Using Other Translations

And the Kohathites set forward, bearing the sanctuary: and the other did set up the tabernacle against they came.
Then the Kohathites set out, carrying the holy things, and the tabernacle was set up before their arrival.
Next came the Kohathite division of the Levites, carrying the sacred objects from the Tabernacle. Before they arrived at the next camp, the Tabernacle would already be set up at its new location.