I would suggest KMR
(stands for Kitten Milk Replacer)
... but it sounds like you've already gotten some. Instructions for how much and how often to feed them are based on weight and age, and are on the back of the container. If you are bottle-feeding them, do not feed them in a "human baby position", with their feet in their air. If you think about it, cats are not meant to eat upside-down like that, and bottle-feeding kittens like this will cause them to aspirate the formula and develop pneumonia. Hold the kitten with its feet toward the ground and their head-end slightly elevated to take the bottle. In addition to feeding them according to the package directions, start trying to wean them. (They may not take yet, but it won't hurt to try.) Get a premium brand canned kitten food and make a soft, runny mash by mixing it with the KMR formula, and offer it to them in a shallow dish/saucer or on your finger tips. Initially, they will just walk through it and get messy (providing precious pictures though!), but eventually they will start eating it. Once they start eating it, gradually reduce the amount of KMR.
If the kittens are not yet going potty on their own, you need to stimulate them to go. Mama cats do this by grooming them all over. What you need to do is, after feeding them, gently rub their bottoms with a soft cloth. They should start "going" with the stimulation; their poop should pretty soft, but not real runny diarrhea.
I would not let them roam free. A cardboard box with soft blankets will work fine, provided the walls of the box are tall enough to prevent them from climbing out. They should be kept warm, as they may be too young to regulate their own temperature well; at 3-4 weeks old, their ambient temperature should be 70-75oF. Over 4 weeks old, they should be able to thermoregulate better. A rough rule of thumb to estimate the age of kittens is that their age in months roughly equals their weight in pounds; in other words, a 1-lb kitten is around 1 month old, a 3-lb kitten is around 3 months old... up to maybe around 6 months. However, keep in mind that these kittens may weigh less than they should according to the "rule," if they have been apart from their Mama for a while.
Definitely call your veterinarian as well as other local veterinarians to see if they will take them in. Unfortunately, many vet clinics will not take them in unless you are going to act as their legal "owner," including taking financial responsibility for them. Also try calling your local animal control/animal shelter; you may have better luck there.
Good luck with these precious babies! Please keep us posted.
