A warm welcome to Mac-Forums. Thank you for your post.
Why not use Apple's built-in app, Time Machine, to back up everything on your Mac including your emails and all your settings, apps - the lot? The total cost is a dedicated External Hard Drive (EHD) kept exclusively for TM backups. You can recover data from it and, when you get a new Mac, transfer everything from TM on to it.
Backing up your Documents to a USB Flash stick, is a risky business - if that is what your are doing. USB sticks are not designed for longevity.
Ian