Product Serial Id Key Field is missing in Outbound Delivery Data Source.
You are not able to find this key because there is no Serial ID key field available in Outbound Delivery Data Source.
You can access the Serial ID details by joining the following two data sources by using Referenced Product ID field.
- Outbound Delivery
- Registered Product General Information
KBA , SRD-CC-MIG-DMC , Migration: Tool , How To