You can see your current grade in a course by clicking the Progress tab in the course.
All questions regarding grading and course content are best addressed in your course discussion forum. It is there that course staff can directly read and respond to your query.
You can read about the progress page course grading in general in our edX learner's guide.
Note: Most edX courses post their grading policy in the course syllabus. Both the syllabus and the discussion forum are available once your class has begun.