Dear Deepika Singh many thanks for this interesting and important technical question. Although I am an inorganic chemist I must admit that I have very little experience with such calculations. It is 40 years ago that I learned this in the course of my chemistry studies. However, I recommend to you a potentially useful reference. Please have a look e.g. at the following articles entitled
1. Stability Constants of Metal Complexes in Solution
Chapter Stability Constants of Metal Complexes in Solution
The full text of this article is freely available as public full text on ResearchGate.
2. AN OVER VIEW OF POTENTIOMETRIC DETERMINATION OF STABILITY CONSTANTS OF METAL COMPLEXES