3 Answers

I would use a Lamb Milk Replacer formula, readily available for sale at feed and grain stores.  It would be the closest formula I think, if not this try Milk Replacer for Calves.  Perhaps in the Wildlife or Zoo industry, there are replacements more specific to deer.  Most important, get the colostrum from its mother, even if she is recently killed, ex. car accident, milk some from her, and feed it to the fawn.  This can also be from a new mother goat, sheep, or cow, with the same benefits.  It provides many advantages, antibodies, fortified nutrition, etc. 

Milk from its mother.Otherwise ask a vet.

Do you have a license to keep a fawn? You can be fined if you are found to have a fawn with no license you know. If the fawn is orphaned, then you need to contact your local fish and game department and have them come pick up the animal so it can be properly cared for by a professional and then released back into the wild.