They need formula (ensure is not good enough for nursing babies)
and they will need to be fed several times a day - the links below will give info on how to feed, what to feed, how often to feed, how to stimulate to go to the pee and poop, etc
and then as they start to slowly wean themselves, you will start offering mice food such as seeds, mixes and blocks
Here are some links on how to care for orphaned babies
http://www.afrma.org/orphanrm.htm
http://www.rmca.org/Articles/orphans.htm
since they are old enough that their eyes are opening, they have a good chance of surviving,
because they will soon start trying solids (and at that point, in addition to hand feeding formula, you can offer a shallow dish of formula thickened with baby cereal, and other foods)
Edit: the above links also give info about foods to offer babies so they will gradually be weaned.
good luck and I hope you post lots of pics