What is the translation of "Na"?
Rashi (in Beha'aloscha) and Targum Yonasan: It means 'Please' (a Lashon of beseaching).
See Rashi there, Bamidbar, 12:1. See also Targum Yonasan there who translates the secind "Na" there as now. Targum Onkelos uses both translations here.