Human amoxicillin and Dog amoxicillin are very different from each other and if your dog requires amoxicillin or any other antibiotics to treat an infection or infections in the dog then you need amoxicillin that's prescribed and made just for dogs.
Dog and Human bodies are different and require different medicines to treat infections and other ailments so always go with the prescribed amoxicillin for dogs.
Otherwise you risk making your dog even sicker.