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Did you ask the designer if he has some original high-poly sculpted mesh or raw 3D scan?
The description is mentioning the model is “low-poly” so that model is not going to print those small details (those need to be in the mesh). What you could try is subdivide the mesh (get more poly’s in) and then try to convert the normal-map to height-field and use it to displace the mesh (hopefully get some of those finer details in the mesh).
If it where a color 3D printer you could probably get away combining the AO map and the diffuse map and get some of those details via the coloring.
Note the model also needs to be watertight (have some thickness/volume), not obvious in the preview images and marmoset viewer is not working for me.
