Hi Uday,
In this case, creating Z-table in ECC and storing all SNC ASN data is one of best option.
Create Z-transaction (copy of Vl31N) such that user will enter PO number then it will fetch the snc ASN data from Z-table.
Here once goods reaches the gate of warehouse, warehouse guy should Z-tcode to perform inbound delivery.(this will create inbound delivery wrt to SNC ASN)
Regards,
Nikhil