Fetch data from child table in doctype to another child table in another doctype

Hello i am trying to fetch data from child table to another but it is not working with me
i want to fetch the “qty” field value in sales order item table at sales order doctype
to “qty_order” field delivery note item table at delivery note doctype but it not working can you help me in this
this is my code

frappe.ui.form.on(“Delivery Note”, {
on_load: function(frm) {

if(frm.doc.sales_order) {

  frm.doc.items.forEach(function(dn_item) {

    var sales_order_item = dn_item.sales_order_item;

    if(sales_order_item) {

      frappe.model.with_doc("Sales Order Item", sales_order_item, function() {

        var so_item = frappe.model.get_doc("Sales Order Item", sales_order_item);
        
        var qty = so_item.qty;

        frappe.model.set_value(
          "Delivery Note Item", 
          dn_item.name,
          "qty_ordered",
          qty
        );

      });

    }

  });

  frappe.run_serially(function() {
    frm.refresh();
  });

}

}
});

Please check the video.