Windows Store [UWP] : error CS0246

Hi everyone

I am trying to develop 3D my application in Windows Store environment. Obviously, you have to use using Windows instead of using System but surprisingly I found that I can't use .Net Core and add Windows Universal into references! Consequently, I meet CS0246 error code which reflects missing namespace :(

Do you know how I can use windows universal namespaces in unity?

Best Regards, Reza