Good afternoon, @nakrami ...
For this type of question, I would highly recommend that you reach out to the folks at UC Davis. For example, connect with their Canvas administrator or someone from their Online Learning / eLearning department. They would (hopefully) be able to help answer this question for you about getting access to your past courses. I took a glance at the UC Davis website, and I found this page:
Canvas Help | Canvas Help (ucdavis.edu)
Hopefully there will be some contact information there that will be of help to you...specifically under the heading "UC Davis Canvas Help".
Best of luck to you as you have those conversations with folks at your school!