Windows 10 upgrade - lost a lot. How can I get it all back?

[Windows Central Question]

Windows 10 upgrade - lost a lot

I upgraded to Windows 10 and lost:
- all of my desktop files
- all of my bookmarks
- Windows Live Mail

I haven't checked out everything yet, but this is pretty important to me. I can live without Live Mail but I sure would like my data and bookmarks back.