Hi. If she's eating little solid food, I would not put her onto cow's milk just yet--this can lead to iron deficiency. I'd either continue breastfeeding a while longer if this is at all possible for you, or introduce formula if you want to stop BF.
I'm not sure you need to substitute one for the other? I stopped BFing my DD a little older, at 15 months, but she has never had more than a few sips of cows milk (or any sort of other milk) when offered. She gets enough calcium through cheese, yogurt etc. What are your reasons for wanting to introduce cows milk?