Location for Linq statement in MVVM pattern

Hi,

I am working on my first WPF app using MVVM application with EF Model.  I have created a View, ViewModel and I have a Model using EF 5.  In my View I've added few combo boxes at the top so that users when select it will populate the rest of the text boxes based on the selection.  Nothing complicated.

My question is where my collection objects should be implemented for combo box bindings?  Should I put this code in ViewModel or should I create something like repository class in Model folder?  Also, how about adding, deleting, updating linq statements?  I guess they probably would be implemented in the same class as the collection objects for combo boxes?

Thanks