In fact, it can be weaned in more than 40 days. Be careful when feeding milk. Kittens may have diarrhea after drinking milk. If they think it is necessary to feed, it is best to use cat-specific milk powder. Baby cat food can be soaked in warm water and given to them.
When a baby enters a new environment, there will definitely be a process of not eating. Just slowly, don't worry, don't always walk around them, give them a quiet environment, an independent space (they may find a dark corner to hide, be quiet, don't disturb them), put food and water where they can definitely see it, and just wait for them to eat slowly.
Cats can use cat litter, but your two babies are too young to be conscious. Take them to the sand basin and let their little ass rub on the sand. Just teach them a few times.
Your baby is so young, I hope they will have a good time in their new home ~