Bindal Agro Chem Ltd — how to demat and sell shares of bindal agro chem ltd

I had invested in bindal agro chem ltd in 1991 and was issued debenture certificate for 25 shares dated 31st december 1991.
Subsequently the debentures were converted in to shares and now i am holding the following shre certificates:
Folio no. Certificate no. No. Of shares
B[protected]
B[protected].[protected]
B[protected]
B[protected]
—
Total 150

I have not been receiving any intimation from the company nor i was getting any dividend/ bonus etc.

I do not know how to demat these shares and how to sell.

I would like to get an early gidance in the matter.

Thank you