Final answer:
The "quantity ordered" attribute should be found in the Order Inventory table, which keeps track of the details of items ordered including the quantities.
Step-by-step explanation:
The attribute "quantity ordered" should typically appear in the Order Inventory table of a database. The Order Inventory table usually denotes the records of items ordered, including details such as order ID, customer ID, the quantity of items ordered, and the date of the order. It is essential to keep track of the quantity ordered to manage inventory levels and understand purchasing patterns.