@DunnoWhatImDoin
Hello, I agree with Miss Lydia, it is probably best to introduce them slowly. I would keep the new ones behind a fence for awhile so that they can see and hear each other for a week or more. Ducks like chickens, have to assume a pecking order, I have only raised ducks so I can't speak on any experience about chickens. After I introduced my 9 runner ducks to my two older ducks, the older ducks herded and bossed the younger ones a bit, but after awhile, the younger ones stuck together and the older ladies did their own thing. Later, my drakes became a problem for the ducks and were rehomed to my friend.
After you introduce your new ducks to your flock, give them time to adjust and try not to interfere with their social hierarchy too much. Of there is excessive aggression you may want to intervene, but for the most part you have to let them work it out amongst themselves. Good luck!