Commentators discussing our Parsha speak about the reasons for the separate section delineated by the inverted “nuns” — “When the Aron (the Ark) would journey, Moshe said, ‘Arise Hashem, and let your foes be scattered, let those who hate you flee from before you.’ And when it rested, he would say, ‘Reside tranquilly, O, Hashem, among the myriad thousands of Israel.'” (Sefer Bamidbar, Perek 10, posukim 35-36)
Preceding these posukim are the posukim which speak about the journey of the Aron and of B’nai Yisrael from Har Sinai to their next resting place, “…a three day distance…” (Sefer Bamidbar, Perek 10, posukim 33 & 34).