Hi Anil,
If the replication is happening from CRM to ECC system, You shall use the BADI -CRM_DATAEXCHG_BADI which is called during the replication. The methods CRM_DATAEXCH_AFTER_BAPI_FILL or CRM_DATAEXCH_AFTER_MBDOC_FILL will be useful to capture the data you need.
I don't understand what you mentioned as "corresponding data" based on which you need to create the sales orders in CRM.
Regards,
Karthi M R.