1. Lodge a Police Complaint for the loss of original documents and take an acknowledgement.
2. Give a Public notification in leading newspapers in English & regional language about the loss of original documents of the property.
3. Obtain certified copies of Sale Deed etc., from the Sub-Registrar's Office.
4. Get the Probate of 'WILL' in your father's name.
5. Apply to the Municipal Corporation of Delhi for change of name in the Khata for the property from your dadaji's name to your father's name, by producing 'WILL' executed by dadaji, alongwith POA in your father's favour.
6.The municipal corporation may insist for NOC from other legal heirs to the property to mutate the property in your father's name in the records of the municipal corporation.
7. After getting the Khata in your father's name, a copy of the same may be given to other departments, to enable them to change the name from dadaji to your father's name in the Electricity bills etc..