Number density of stars on the Galactic plane The number density of stars (e.g. the number of stars per cubic parsec) is given by 
$$N(z) = N(0) e^{-|z|/h}$$
where $z$ is the height above the Galactic plane, $h$ is the scale height for a specific component of the Galaxy, and $N(z)$ is the number density at different heights above the plane.

The scale heights for the thin disk and thick disks are:


Halo stars: $h=3\textrm{kpc}$
Thick disk: $h=1.5\textrm{kpc}$
Thin disk stars: $h=300\textrm{pc}$
Thin disk gas: $h=100\textrm{pc}$


Unfortunately I cannot find the values for the number density at the galactic plane: $N(0)$

Do you have any references in which I can find these numbers?
The number density of stars is not well constrained, because it hinges critically on the behaviour of the stellar mass function at low stellar masses. Low-mass stars tend to be dim and hard to detect. What is reasonably well constrained, instead is the mass density of stars, where low-mass objects contribute little, even if their number is large.