Kartik, can you do us a favor, and not open new separate Forum posts if you are relating to another post?
We guess this question belongs to your other post https://synesty.freshdesk.com/support/discussions/topics/11000020643
For example you can view your existing forum topics here.
To your question:
Is sounds like the field unitname(productname) comes from WeClappGetWarehouseStock but it is not yet in your datastore schema.
To automatically add new fields to your datastore schema you can try enabling the option: autoExtend schema in step SpreadsheetDatastoreWriter.