Which serial number are you referring to? Are you collecting it with a UnDP or is it some place in the Orion UI that you are seeing it? If you can tell me how it's being collected I can point you to it in the DB. Keep in mind that the way it's stored in the DB is not necessarily straight forward from a query standpoint.
You can always try and get it using the Report Writer and then view the SQL query that it's using to reverse engineer where the data is stored.