My understanding is finding someone like a psychiatrist or psychologist, in some cases I’ve heard therapists helping to get in touch with people you need so you can get an evaluation

I went to a psychiatrist and pushed them for testing and eventually I was scheduled and diagnosed.

Like the other comments said. You keep pushing for it to happen. Here's a tip: If a doctor refuses to give you something you say you need, force them to write it in your notes or medical record. Just say "Since you are denying me to test me for Autism, please put that in my notes and why you are refusing it even though I insist on it" Or something like that. Usually the doctor will backtrack and quickly get you those tests you need done. It works for me

Find a clinical psychologist that can diagnose and request to be assessed. for me, i was able to see the same person that diagnosed my adhd so i got lucky. sometimes they have to rule out things like depression, anxiety, and other problems first. but if whoever you see says “its just anxiety” and you know its not, listen to your gut. i wish you luck

There's a saying that is "the squeaky wheel gets the grease" keep advocating for yourself to get proper testing. I only just got diagnosed with ASD this past year and I'm 30 and brought it up ad nauseam to my psychiatrist and therapist until it got done