I noticed that you have performed Share Topology operation between the 2 bodies. Since we need to create additional bodies, unshare all the faces and edges.
Select the 3 inner layer faces of any body. Then right and select Copy, and then Paste. This will create a new surface body for the inner 3 faces.
Hide the 2 solid bodies, then click the Pull tool and select all the 3 faces and pull them by an appropriate distance. This will create a thin solid body. You may want to enable Symmetry option from the Options panel if you would like to pull the faces symmetrically on both sides.
Next, display all the 3 solid bodies and click Interference tool from Prepare menu and click the check mark button to complete the operation. You will now see the thin layered volume between area 1 and area 2.
Follow similar operations to create thin layered body on the outer side.
Regarding meshing, since the geometry is modified, you will have to remesh the model. Additionally, since you now have thin bodies in the geometry, you will have to ensure minimum 3 mesh elements across the thickness which will increase the mesh count.