where can I learn more about biasing the fet for mic.I have only a multi meter.Do I need to buy scope ?
That tells me, quite certainly, that you didn't bother to read through even half of this thread..(?)
Otherwise, you might have stumbled across this:
https://groupdiy.com/threads/open-source-diy-mic-project-ors-87-stripped-down-u87.86814/post-1156442