I just ended up with baby Field mice. An the mom got killed so how do I feed them or does anyone know how I can find a mom field mice who is nursing

You might consider contacting a local vet. You can use Google to learn how to make formula for them and bottle feed (or syringe feed). We did this for ground squirrels 2 years ago. They did well and lived into adulthood. They are very similar to mice.

You might call Petco to see if they have any recommendations