They are to keep his requirements and the requirements of the whole congregation before the Tent of Meeting, to do the service of the tabernacle. Bible see other translations

“before the Tent of Meeting.” This could be translated and understood as “in the presence of the Tent of Meeting,” that is, inside the curtain wall that surrounded the Tent of Meeting. The Levites were to minister inside the curtain wall, doing all the tasks necessary to keep the whole Tabernacle system going. There was incense to burn, bread to bake and change out, firewood to bring in and stack, water to draw, and many more such tasks.

Commentary for: Numbers 3:7