Here's my tutorial for doing Cataclysm Weapons, it is long, but for someone like you who doesn't have any idea how to proceed, it might be best to view the whole thing.
I do not visit this forum very often anymore, busy with real life and a few other projects at the moment.
If you don't want to learn how to convert, you can download my already converted model files from here:
http://emudevs.com/showthread.php/140-MoP-5-2-0j-and-Cataclysm-World-M2-Files-for-WoTLK
The Downloads on ^That page has Cata to MoP 5.2.0 data. After you download it, just pick out what you need from it if you don't wish to use the full thing.