To treat and prevent fleas and worms in dogs, use Comfortis Plus

https://www.ebay.com.au/itm/275378432500
Comfortis PLUS offers three-in-one parasite protection for your dogs. This delicious chew treats and guards against intestinal worms, heartworms, and fleas. The treatment is safe for dogs with flea allergy dermatitis and provides continuous flea protection for one month. We offer the lowest market price and the quickest delivery.
https://www.ebay.com.au/itm/275378432500