how to create a pair from a group?

Hello and welcome to the forum, Amit.
I understand your problem, – it can be difficult with young fish to determine which female is the right one, – and I would say that there is a good chance that any female will do :).
There could be also the situation that the reason you are not really seing any preferred female is that they have perhaps not quite reached the grown up mature state as the male.
I am sure you can choose any female, and after a little while the pair will breed together. It may take a little while, especially if the female is very young and perhaps only just reaching maturity.

Or you could wait a little bit, and watch the fish careful and over some days see if the male seem to be more attracted to one female than the others. The problem then is to catch this precise female, – and once scared and on the run … :unsure: its so difficult.
I can do it, but I have many years of practice, and I have the fish in small tanks. I will cheat them and move in very slowly when the one I want is swimming happily by the front glas 🙂 … but I know this is not always possible.

So if you feel its easier, dont hesitate to take any female, – eventually they will ‘bond’, they are not particular about partners, although of course sometimes you do get a harmonious couple that it is a pity to seperate.

There is another possibility. With me you spawn Paros in caves when males and females in the cave to spawn pull back, you can put together both cave.