If I were in your situation I’d ask a lot of people for recommendations for a therapist. Especially if this is your first experience with therapy, it’d be good to get different people’s opinions about who is good, why they think that person is good and what they think are good indicators that someone will be good to work with. That will help you tell which recommendations would be the most helpful. I hope you have a lot of acquaintances that you would feel comfortable asking for info, as there are a lot of people out there with ADHD, but unless you bring it up, you might not even know you have it in common with them, or someone they know.
I agree with ers375 that an intake session might be a good way to start. They are often free, or would be covered better by insurance (than a mental health therapist), if you are talking to someone affiliated with your regular doctor’s office. That person wouldn’t probably be who you’d be seeing for therapy, but they’d hopefully have some good referrals for you. Then when you get the referrals, ask for whatever introductory sessions the therapists offer, so you can get a feel for who they are before even committing to a therapeutic relationship with them.