I saw “Back Up” listed in the file menu. However, I was wondering if Scrivener has a ‘Auto Back Up’ function for each project (e.g. default save: Desktop/Works/Novels/project name folder/ | back up save: computer/thumb drive/works/novels/project name folder/). Something like if I click ‘save’ from ‘File’ menu it would save the project to both locations or is the 'Back Up" a manual only thing?
Yes, it does have an automatic backup feature, and very likely it’s already got your back without you knowing. In the Preferences/Options window, check the “Backup” tab for configuration. By default it backs up five copies on a rolling stack, making a new one each time you close down. It’s worthwhile to tune those settings to your work habits. Some people leave projects open for weeks, and in those cases only backup up on close means going without protection unless you make your own periodically. I work that way myself, so I use the option that creates a backup whenever Ctrl-S/Cmd-S is hit. I’ll press that a few times throughout the day if I’m doing a lot of work. I’ve also upped the maximum to 25, and pointed my backup folder to Dropbox so that backups are distributed amongst my computers as well as the main Dropbox servers, automatically. I also disabled backup on close, because I open and close many dozens of test projects throughout the day that I have no intention of keeping—but I’m not a typical case.
Note that if you have Time Machine or something similar, it will keep backups of your backups going back as far as it has disk space. So you aren’t limited to just what Scrivener itself maintains.
For long term archival storage, though, it’s best to have some kind of non-volatile off-site storage, too. Dump everything you care about to a USB stick and throw it in a safe deposit box, for example.