Newbie question regarding Passport Ultra

Guys - I have a Passport 2TB ultra bought in 2015. All this time it’s been happily backing up my files. Or at least I think it has. I’m about to upgrade from Windows 7 to Windows 10 and I want to make sure everything is backed up. It appears that some files aren’t backed up at least according to the WD Smartware app. Anything I can do about this? Some of these files date back a few years, some are recent.

Also when I go into the external drive itself some folders won’t open saying the file or directory is corrupt or unreadable. Is there a way to fix this so I can see what’s back ed?

Many thanks