cannot get quiz grades into assignments

I am unable to get my quiz grades from Forms into the assignments in Teams.  The quiz has already been autograded by Forms.  So I create an assignment, add the quiz, but none of the grades get imported.  The problem is how to import grades into the assignment so it shows in grades.  Note, I do not want to create the assignment first because the quiz is embedded in a Stream video and not available separately.  How to do this?