Yes. When your puppy is 3-weeks old, it's a good time to start weaning them off the mother's milk or milk replacer. However, it's always a good idea to consult your vet before you introduce your pup to solid foods. Also, it's important to make the transition gradual and stress-free. Take your time to introduce small amounts of solid food into your furry friend's diet. You could also try giving your pup semi-solid food, such as porridge, before switching them to veggies, fruits, and meat.