Bacterial Growth Formula
Either; they're identical to the units of $N(0)$.  In $N =N(0) e^{kt}$,


$t$ has units of time (days, minutes, whatever you have chosen)
$k$ has units of (1/time) (inverse of $t$'s units)
$kt$ is thus unitless, as is $e^{kt}$
$N$ and $N(0)$ have the same units.