If there are materials from earlier courses that you wish to save, there are two quick and easy options - or you can do both:
You can create a course backup file and save it to One Drive or other storage. This file will later need to be restored within Moodle before you can pull out individual items, but it maintains the organization of the files more exactly.
You can download all instructor files and save the resulting folder full of files to your Google Drive or elsewhere. This allows you to pick-and-choose to re-use individual files but does not maintain the course structure.