Get it to the vet quickly. Don't feed cow's milk, you'll have to get kitten replacement milk. Be sure she's warm. Check for any ticks or mites, or otherwise any wounds that will need treatment.
If you think the momma if nearby set the kitten in the garage in a box (while watching ofc) and if the kitten cries she may hear.
If you think the momma if nearby set the kitten in the garage in a box (while watching ofc) and if the kitten cries she may hear.