Hi Smita,
To show/bring any field in the form template of a particular BO (in this case, Production Task), the field should be available in the BO. I.e. If the customer part number is not available in the Production Task BO then it cannot be brought into the form template.
You can extend a field in the Production Task BO and fill the customer part number in it. Then after add this field to the form template.
Best regards,
Sathia