found a baby mouse

Question
Today my cat brought in a nest with a baby mouse init.  At first I thought the baby was dead but after checking it over it started moving.  It's so tiny, eyes closed and barely any hair on it.  Sadly I found the other baby in the yard and it wasn't alive.  I checked on line and found information on how to give it electrolytes and I ran up andgot the KMR formula and I'm trying to feed it.  It's moving around a little and I put it in a box with a heating pad on low under a little soft blanket.  I just don't know how or really what to expect.  I'm not even sure if it has fur because it looks mostly like it has just skin.  Is there anyway to know how old this baby is?  Also how much should I feed it and should I feed it the electrolyte or the formula and ow do I know if any is getting swallowed because I cn't tell if anything is getting into it's mouth let alone his belly.

Answer
Dear Aleda,

Most of your answers are in the following question from a couple of days ago:

http://en.allexperts.com/q/Mice-3824/2013/4/guide-orphan-mouse-pups.htm

It is the season to find orphan mice.

The way you can tell if a little pinky mouse is full is that you can see the band of milk in its belly right through its skin.

If it is mostly skin, it is under 5 days old. Compare to these photos:

http://www.thefunmouse.com/info/daybydaybabies.cfm

If there are any questions I have not answered, please let me know.

Squeaks,

Natasha