we have been in the USA for 20 years, but are thinking of going back but my drivers license as expired for quite a while now what do i do to get it renewed

The previous answer still stands: Going back to the UK

yes but its the old paper one

https://www.gov.uk/exchange-paper-driving-licence

So was mine but I simply applied using the usual form. (I returned in 2016 after 29 years out of the country)

I had a very similar experience, and received the new license within about a week.

yes but I’m 77 do I have to take a test

No, but you do have to renew your DL every 3 years (you can't renew it until you're a UK resident):
https://www.ageuk.org.uk/information...bbies/driving/
https://www.gov.uk/renew-driving-licence-at-70