You can check Data extraction configuration in object: de_config (object ID) and check if you have attribute with 'de_datawarehouse_nam'. If you don't find these details, you are on older version of plug in. Also, From the screenshot you have shared, it seems like a older version of Data Extraction plug in. I remember the updated version does have provision to query from data warehouse. Contact CA Global delivery for updated plug in.
External database name: that was designed to read the data from niku database and write the data to external database (which can be configured in CSA).
Regards,
Praneeth