Ask your Vet. Ask your friends with dogs, the ones with nicely behaved dogs. Ask complete strangers you meet who have well behaved dogs.
This site might help you find someone. Dog training is an unregulated business and you can find people with outdated ideas or no training at all, but word of mouth and membership in the above, while no guarantee, may help.
Ask if you can audit an ongoing class. Watch how trainer and students, that's YOU, not so much the dog,
interact. I have one trainer that I always recommend to folks by telling them she treats us, the humans, like a dog. Dogs don't do something wrong for spite or because they are stubborn, right? Dogs do something wrong because they don't get it yet. Well, we humans are the same but I've had trainers who were lovely with the dogs but nasty with us humans. Ironically this particular trainer is from Montreal but doesn't live there now, your loss, my gain. LOL.