John Gill Commentary Numbers 4:31

"And this is the charge of their burden, according to all their service in the tent of meeting: the boards of the tabernacle, and the bars thereof, and the pillars thereof, and the sockets thereof," — Numbers 4:31 (ASV)

And this [is] the charge of their burden
What should be committed to their care and charge, and they should bear and carry:

according to all their service in the tabernacle of the congregation ;
which was assigned to them as their part, and which was very heavy and cumbersome, and therefore they had wagons allowed them, (Numbers 7:8) ;

the boards of the tabernacle, and the bars thereof, and the pillars
thereof, and sockets thereof ;
all these belonged to the holy and to the most holy place; see (Exodus 26:15–37) .