Hello
This information is not stored on any table. Please take a look on my answer on thread MD09 Pegged Requirements History | SCN.
The only way to have a link between the sales order and the production order it to use a make-to-order planning strategy (such as strategy 20). This way, the production order will be linked to the sales order special stock and you will find the sales order number on CAUFV. However, this is not a simple change and you must discuss it with your business users.
Regards
Caetano