Numbers 3:34

And those that were numbered of them, according to the number of all the males, from a month old and upward, were six thousand and two hundred.

Cross-reference

Numbers 3:15 is the command to number Levites from a month old, directly fulfilled by this verse's count of Merari.

Numbers 4:44 counts only Merarites aged 30–50 for service (3,200), a subset of the 6,200 total males here.