In Greece only licensed tour guides are allowed to escort visitors through ruins, museums, etc. Their licensing requires years of rigorous studies. Currently I think the going rate is about €60 pr hour, usually 2 hour minimum, for groups up to 4-5. When I first visited Nafplio 20 years ago, local agencies were running day tours with a licensed guide, covering Mycenae & Epidaurus. Alas, havent seen this lately.
Google -- IF you specify Licensed - does give some links to investigate: https://www.greecetravel.com/tour-guides/argolis/index.html
http://www.olympictours.gr/guiding-services/private-guidance-in-mycenae (this one explains the value of licensed guide in experiencing a complex site like Mycenae
https://www.tourist-guides.gr/guides/list-of-licensed-tourist-guides/ -- has a long list of licensed guides but mostly in Athens -- he only one with address "argolis" ( = Nafplio area) only lists a phone #, no email.
You are probably going to get enthusiastic comments about a wonderful day out, but close reading will reveal that their "guide" was a driver had a lot of anecdotes & took them to a nice lunch place but who handed them a brochure at the entrance to ancient sites, but was not permitted in..
