Moving Materials from one library into another

We have a materials library in Creo that goes to our Windchill App server directory but the contents of this folder are not inside a Windchill library if that makes any sense, its more like a local library thats shared. Creo users can get to it. Now, we also have a materials library in Windchill, the problem is, I cannot upload my Creo materials library objects, into the Windchill Library, when I try to do so it says the file is not unique. When I try to find the file in Windchill it does not exist. How do I work around this?