C# how to access each other form objects

Below this code I'm trying to figure out how these forms can freely accessed their both objects. In these code, 

 - ITEMCount can access the objects of SIMSProduct
 - On the other side although SIMSProduct can see the objects of ITEMCount
(There is no argument given that corresponds to the required formal parameter 'view' of 'SIMSProduct.SIMSProduct(ITEMCount)')

//Form that use SIMSPRODUCT controls
        public partial class ITEMCount : Form
        {
        SIMSProduct  _view;
        public  ITEMCount(SIMSProduct view)
        {
            InitializeComponent();
            _view = view;
            DisplayQuantity();
        }
        }
        // Form controls that been accessed by ITEMCOUNT
        public partial class SIMSProduct : UserControl
        {
        ITEMCount _view;
        public SIMSProduct(ITEMCount view)
        {
            InitializeComponent();
            _view = view;
        }
   
        }

        //Code for calling the ITEMCount form
            new ITEMCount(this).ShowDialog(); // Belongs to SIMSProduct form

        //Code for calling the SIMSProduct form
            var obj = new SIMSProduct(); // this where error point out
            obj.Dock = DockStyle.Fill;
            panel3.Controls.Clear();
            panel3.Controls.Add(obj);