Hi @cew374,
If your school/institution has enabled the option, you could download your course as an epub file. Be aware that file may not be comprehensive, and definitely would not include any of your submissions.
At my institution, we allow students to log in and access courses up to 7 years after they are completed, so there's quite a long timeframe there. Realistically, even if you were able to download a course like faculty could, you'd need a Canvas instance to put that content back into, as the download file itself is not really meant to be a usable thing on its own. I think you may want to talk to someone at your school to find out what their access/.retention policies are, and also see if they have any suggestions on downloading content for your own archival purposes.
I hope this helps a bit!
-Chris