Rashi on Numbers
ואתה הפקד את הלוים BUT THOU SHALT APPOINT THE LEVITES OVERSEERS [OVER THE TABERNACLE etc.] — Understand the word הפקד as the Targum does: ,מני “appoint”; it (the word מני) is an expression for appointing a person to control that thing over which he has been appointed; similar is, (Esther 2:3) “and let the king appoint (ויפקד) officers”.
Sforno on Numbers
ואתה הפקד, the commandment to count them is repeated to make clear that they are in a class by themselves. The reason was that only this census rated as a holy activity.