If I understand your question correctly, you want to know how to find the batch number of the piece part that was issued to make your finished good, using the serial number of the piece part. To do this, go to T-Code ZPPORDISS and put in your Production Order number. This will give you a list of everything that was issued to your job. From there you can find the serial number of that piece part number and see the batch number associated with it.
I hope this helps.
~Amelia