What you need to do to integrate new chix: set up a situation called "see but don't touch." So the chix are all side by side during the day where they can see each other but do no harm to one another. We did this in adjacent yards for about two weeks. Each group had their own separate roosts, in separate buildings (coops). There was a gate between them. One day we left the gate open. None of them noticed. When they did, it was just natural for them to all become one flock. Then one niht we shut the door to the babies' coop and they roosted on the floor of the big girls' coop. Over time they found places on ghe roosts.
Adapt that info to your situation. Find what works for you.
Adapt that info to your situation. Find what works for you.