Help with Monday.com automation

We want to use Monday.com to run the various operations in our company but have some challenges to create orders with subitems. The issue we have is that we can only download product information as items rather than subitems (as Monday.com does not allow subitem import). This project is to look at how we create items and then automatically turn those items into subitems below the order. The order has an order number which is unique and all the products on the order are referenced by the same number.

If this is not feasible, then would there be other (not manual) ways of managing the data. I have attached a pictorial representation to help.