Sandeep Kumar ,In nowadays , each manufacturer has own shanks of the blades set which is his intellectual property. That is why you will never find fir tree slots dimensions of the modern turbine. This is corporate information.
On my mind , find information about fir tree slots of the old turbines is the only available arrangement for you.
I can suggest following: in USSR all-Union standards have been developed.Try to find: "ОСТ 108.261.08-84 Профили прямозубчиковых хвостовиков и пазов. Конструкция и размеры"