So I had this issue a few days ago when I was trying to setup the Zombie Map making Tool from UGX and the error I had was that XMODEL.DLL was missing and at the time I had no idea how to fix it, I tried uninstalling COD and re-installing and googling it and it actually came up with this forum but no actual guide on how to fix.
So I thought I would make this post to help people who may have this issue in the future.
So To Fix:
Install Cod for the first time
Play the game, if required you should be prompted to install directX
Close the Game.
Search google for - Visual Studio 2017
Install it and Select Visual C++ & Unity
Follow this tutorial on how to do the rest:
Download the all in one pack
Cut/Paste the .RAR file to your COD Root Folder
Open in WINRAR
Select the files & Folders not include the ...
DRAG & DROP
Head Straight to the Launcher Program, Open as Admin and Hit Converter.