You should go by her current weight ( and taking into consideration if she is overweight, active etc) to find out how much nutrition that a dog needs.
I have raised Josie on Origenz dry biscuit since she was young. It's a pretty high protein, Canadian made, grain free product. I give her 1/2 cup twice a day , on a regular schedule. She is fairly active, weighs 36 pounds each month, her poop is regular and not gross looking( considering it's poop).
Josie is 10 years old this July, and still acts like a pup! She has fantastic skin and her coat is shiny! Loves going camping in the RV, and can not wait until next month. It's been a long winter.
Start your dog slowly, however, buy a small bag of your choice, and mix it in a bit more each time with the canned product, until you are all dry. Watch her well and see if she tolerates it.