What to do if i am addicted to opiates, need help, and don't know how to tell my parents?

See a counselor: You need to get help, and if you are 36 years old, you don't need your parents' permission or involvement to start treatment. A counselor can help you with learning ways to inform your parents, and it would probably be helpful for them to be involved in family therapy and/or Alanon (a family 12 step program) as well. The important thing is getting into recovery asap, and overcoming guilt/shame.

You are 41 and still: Can't talk to your parents? My experience is that parents, even when not told anything, know something is wrong. If you need help, get it, and don't worry about telling them. Your counselor can assist you when you are in treatment. The important thing is to stop, and with opioids that needs professional help most of the time. Odds are that it will not be as bad as you think it will be.