How to transfer land to my mother post my grandmother's death, given informal adoption in 196?

I have a question regarding the adoption of my mother. In 1969, when my mother was 7 years old, she was adopted by my grandmother, who was 34 years old at the time. My grandmother, who did not have children of her own, adopted my mother, who is the daughter of her own brother, then 37 years old. After her adoption, my mother married my father in the same village. Following their marriage, my father resided permanently with my mother's family. Twenty-five years ago, my grandfather passed away, and recently in 2024, my grandmother passed away at the age of 89. We now wish to transfer 3 acres of agricultural land of my granny's into my mother's name. We have obtained the death certificate for my grandmother, but we do not possess a legal adoption document due to lack of awareness. What are the necessary legal steps to obtain the adoption documentation and transfer the land into my mother's name? Thank you for your guidance on this matter; it would be immensely helpful to resolve it legally.