Orphaned kittens are highly dependent on a special formula to keep the nutrients they need to thrive. You need to keep in mind that kittens are dependent on liquid nutrition from birth up until around 4 weeks.
While an ideal food source is the mother’s milk, you will also have to learn how to make kitten formula to ensure that these kittens get sufficient calories and nutrition in the absence of their mother’s milk. Yes, knowing how to whip a kitten formula is also a good skill for emergency feeding.