I thought it was very easy to find. I go to any group that has the id and click on it and I will get something like this for the account:
i:0#.w|domain\userid
And I found it was way harder. I also tried the Get_SPOUser commandlet. It only gave me the userid part but not the token part.
Then a colleague asked me to try:
https://yourtenant.sharepoint.com/_api/web/currentuser
And in the LoginName field I found the answer.