Can someone enlighten me to the sources or how to do it

I'm not certain I follow your question. I'll assume you don't mean "How do I estimate a certain number of cards when I cut" or some such, as that wouldn't be specific to any stack.

So, your question could mean a number of things. Here's answers to most of the things it could mean...

If your question is "How do I determine how many cards someone cut off when using Stebbins?" then the answer is: this can be found in a free public domain book called "Si Stebbins, Card Tricks and the Way they are Performed" (a simple Google search will take you to it.) The part that explains it is called "Weighing the Cards."

If your question is "How do I know how far down from the top a certain card is?" then the answer is: it's in the same book mentioned above. The part that explains it is called "Knowing the Position of a Card from the Top."

The above being said, there are better ways (I feel) to do the above. One of them is Tom Gagnon's method (fair working--it requires putting work in the cards) published in Trapdoor #65 (apparently, it's also published in his "Too Hot for the Devil," but I don't have that one.

If your question is "How can I position a named card at a named number using Stebbins?" then the answer is: Thomas Baxter figured out an ingeniously simple (one you get used to doing the mental calculations) method in "A Card Merely Thought Of." The part that explains it is called "A Formula for ACAAN." If the named number is divisible by 4, this method is simple. Not divisible by 4? A tad bit more complex, but nothing that can't be done in a couple seconds tops.

Thanks a lot for the detailed input. It will be very much helpful. Will check them all.

You can find some useful info here:

https://trickshop.com/stebbins.html

Thank you and yes I have this

The method I was looking for is in scarne on card tricks