Associate these lines with button click.
#if NETFX_CORE
string productID = Windows.ApplicationModel.Package.Current.Id.FamilyName;
Application.OpenURL("ms-windows-store://pdp/?ProductId=" + productID);
#endif
Is something described here not working as you expect it to? It might be a Known Issue. Please check with the Issue Tracker at issuetracker.unity3d.com.