Do I need to download the files and the zoom videos if I want to have a back up of them? How long and how big can these files be saved on canvas?
You'll need to ask those questions to the people who manage Canvas and Zoom at your school as they manage data retention. If I had to guess, your Canvas content might stick around for quite a while, but Zoom cloud recording will probably have a shorter life as your school needs to clear out space in the cloud environment. I do think that Zoom sends you a warning email before cloud recording get deleted however.
Retrieving data ...