I believe you said the dog is 9 months old? And it has been wormed twice? Did you realize that you can bring a stool sample into the vets and have it checked? After testing, they will prescribe the proper wormer for your dog and the exact dosage to give him, without an appointment. At least start him on a worming program.
You will probably need to worm him every 2 weeks, just as if he were a puppy, since he has not been properly vetted. Worming is one of the more reasonable aspects of pet care and is so necessary to maintian a healthy dog.
Also, most likely, when you bring him in for his appointment, they will start his shots over, just as a puppy, since he was never vaccinated beyond that first set of shots.
Please follow up on this fellow, he deserves a better life than he has had.
Only worm a dog when they need it. I do a fecal on all my dogs every year, or sooner if they’re at the vet for something else. The vet will tell you what kind, if any, worms they have and give you a medication for that type of worm. Some people just worm so many times a year, but I don't like putting any unnecessary chemicals in my dogs. As for the puppy shots there is reason to have to redo the series they don't need a series in the first place. I would highly recommend you do a titer test to make sure he even needs any shots before you give them and if you do give shots wait until he's up to weight and healthy. There’s a warning on vaccines to not give them to unhealthy animals, but many vets ignore it and can cause problems. http://www.pets4homeopathy.com/articlesvaccs.html