What did you do before bringing the puppies home? I read the question and it looks like you just brought home three strange animals who run around and make noises and smell ever so odd and unfamiliar.
When we already had a male dog and decided to buy another male dog, we naturally went to see the newborn puppies a many times. For only two of these visits we brought our older dog with us to the house where those little puppies were growing up. We let our dog have a smell sample of the puppies, and he did, but he was also wary of the mother dog and most of the time he simply steered clear of the puppies and their mother. However, with our clothes the smell of those puppies came home to us after each visit, and on those two visits our older dog got a firsthand experience of the puppies and smells of that house and all.
When those puppies were 8 weeks old we went to get our puppy and we took our older dog with us for the trip. So he was one of us, bringing home a new member of our family. When we got home, at first we did not let the puppy on the floor, but kept him in (my wife's) lap so that our older dog could take a proper smell sample of the newcomer. The older dog was not quite happy about the new dog, for it was too noisy and far too full of energy while awake. However, he accepted the puppy. Of course the old dog had to bark and growl at the new dog at first, as of saying "we are not friends yet!"
The second day of the new puppy at home with us they were already sleeping this near to each others:
And ten days later they already sleep in the same basket, even though the puppy had a basket of his own, he preferred the warmth of the older dog.
Now, when you bring a new animal in your home, do not expect your older animals to accept them just like old friends. They don't.
Get smell samples for your older dog. If you can't take your older dog to the puppies, at least take a towel there for a few days and then bring the towel home (with the smells) a week before the puppy/ies.
Take your old dog with you when you go get the puppy/ies home.
Keep the puppy/ies in place at first, for the old dog to come safely close and sniff the newcomer(s). Do not let the puppy/ies to run free around your house right away.
When your older dog barks and growls at the puppy/ies, don't panic, don't get nervous, but keep calm and see what happens. Your dog mirrors your feelings, and will eventually calm down too.
I'm sorry but I don't have experience what to do, if these steps were not taken and the older dog wants to attack your puppies. I have no answer to that :(
Having said that, there is one thing I would try first of all. For dogs have this "Get lost, I was here first!" mentality. So, take your old dog for a long walk. While he is away, let somebody play with the puppies so much that they get sleepy. Before they fall asleep, let them eat well. They should be sleeping by the time the old dog returns, and now the puppies are the "first ones here" and your old dog is the one coming in. The puppies are safe (from the old dogs point of view) to go near and sniff. And they were there first... No guarantees, but worth a try.