I can give ypu a comparison size tree and approximate age. The Pecan in my sons back yard was planted in the 1950's by my sons great grandmother. A tornado blowed it over in 2024. The dia was a bout 38 in which would give it a circumference of approximately 9,9ft. the tree would have been approx 70 years old. So my best guess is your tree is just under, or about 70 years old. Not taking into account the difference in growing conditions or region the tree grew in.