Bindal Agro Chem Ltd — Did not recieve interest or shares against convertible debentures

My father has 25 convertible debentures of Bindal Agro Chem Ltd issued on 31st December 1991. He has not received any interest or converted shares against them. It says that the debentures would have converted in 1992. Since then, the company has changed its name to Oswal Greentech.
Kindly help us cash them out or get equivalent shares against them.

Details of the debentures:
No of Debentures: 25
Date of Issue: 31 December 1991
Folio No:[protected]
Debenture certificate number: 84797
Name of Holder: Chand Krishan Vaid