OK - it became a bit confusing. Orthotropic properties you would need to give to the honeycomb if you were approximating this structure with a single 3D plate/volume part thus using 3D brick elements, but if you represent the actual honeycomb geometry in 3D then you do not need that (Orthotropic). This can be called homogenisation of properties. See here for details for this 



So for using the actual honeycomb geometry (shell geometry)

The skins and your core are made of isotropic aluminium which you can find the Young's modulus on say mat-web or from the manufacturer (say something like ~ 73 GPa). Density you have (~2800 kg/m3), so that is all you need, with Poisson's. Thickness as shown in the tutorial you can assign to the surface parts.


Use also appropriate connection between them (Say bonded contact or something reasonable).