query for showing columns from various tables, grouping and showing calculated field in each row of the result
Basic is that you have all Tables set and also defined the relationship.
Then you add a new query.
Then you pull in all Table that you need, if your relationships are correctly set, all tables should ha a connection.
Now you pull all needed columns into the part below
and add a column that has the difference betwenn qty ordered and inqty

Now you have a corect query to run.
As SQL it looks like
SELECT ITEM.item_name, STOCK_IN.description, ORDER.date_order, ORDER_ITEM.[qty_ordered]
, STOCK_IN.in_qty, STOCK_IN.in_date, [qty_ordered]-[in_qty] AS qty_left
FROM ([ORDER] 
      INNER JOIN (ITEM 
       INNER JOIN ORDER_ITEM ON ITEM.id_item = ORDER_ITEM.id_item) ON ORDER.id_order = ORDER_ITEM.id_order) 
       INNER JOIN STOCK_IN ON ORDER_ITEM.id_ord_item = STOCK_IN.id_ord_item;

For your query to have the complete quantity for all orders
SELECT ITEM.item_name, STOCK_IN.description, ORDER.date_order, ORDER_ITEM.[qty_ordered], STOCK_IN.in_qty, STOCK_IN.in_date, [Sum1] AS qty_left
FROM 
    ([ORDER] INNER JOIN (
                                           ( ITEM INNER JOIN (SELECT ORDER_ITEM.id_item
                                                                       ,SUM( [qty_ordered]-[in_qty]) AS Sum1
                                                                       FROM ([ORDER] INNER JOIN ORDER_ITEM ON ORDER.id_order = ORDER_ITEM.id_order) INNER JOIN STOCK_IN ON ORDER_ITEM.id_ord_item = STOCK_IN.id_ord_item
                                                                       GROUP BY ORDER_ITEM.id_item) qtysum ON qtysum.id_item = ITEM.id_item
                                           )
INNER JOIN ORDER_ITEM ON ITEM.id_item = ORDER_ITEM.id_item
) ON ORDER.id_order = ORDER_ITEM.id_order) 
INNER JOIN STOCK_IN ON ORDER_ITEM.id_ord_item = STOCK_IN.id_ord_item;

Result: