C# .xaml transfer an Object from one window another

Question

I have a form "SprocketOrderForm.xaml" window. I push a button to open a new window, "SprocketForm.xaml". In that window when I click submit it will create a new "Aluminum" object populated by the textboxes in "SprocketForm". Now I need to get that new object back into a listbox in "SprocketOrderForm". I've been stuck on this for a while now.

"SprocketOrderForm.xaml"
    private void btnAdd_Click(object sender, RoutedEventArgs e)
        {
            if (rbAluminum.IsChecked==true)
            {
                SprocketForm sf = new SprocketForm("Aluminum");
                sf.Show();
                lisbOrderList.Items.Add(sf.objAlum);
            }
        }
    


    "SprocketForm.xaml"
    
        private void btnSubmit_Click(object sender, RoutedEventArgs e)
                    {
                        if (sproc=="Aluminum")
                        {
                            AluminumSprocket Steel = new AluminumSprocket(int.Parse(txtbItemID.Text), int.Parse(txtbNumberOfItems.Text), int.Parse(txtbNumberOfTeeth.Text));
                            objAlum = Steel;
                            this.Close();
                        }
                    }