Problem importing 3D model

I'm an IOS developer and I'm new to 3D modelling. I tried to import 3D models which I've downloaded online into my Unity Vuforia project by doing an 'Import Asset'. When I add the model into my project, it appears as grey in colour. I understand that this is because I haven't apply texture and other materials to the object.

From the zip file which I've downloaded online, I'm given a bunch of diffuser, normal, specular files but I have no idea how to link it into the 3D model. Is there any ways to automate this process ? Sometimes a 3D model would request for 10-50 materials but the naming of it is completely different from what I find in the zip file. How do I match them ? I am stuck with this problem for a couple of days already, appreciate if someone could help me out.