How do I update old blender projects to the newest version of blender? I have some unfinished projects I want to get done and I want to update to the newest blender version, but, when I install the new one, all my old files don't seem to update, they still say .81 when opening... I'm confused... and I don't know  how to fix it... because it auto updated when I went from 2.79 to 2.81, and I have tried uninstalling blender and reinstalling it, but to no avail.
You don't need to update your .blend file.
You just need to open them with a newer version of blender.
Uninstall older version of blender and install new one (you can also install a new version without uninstalling the older one).
Start new blender version (to open the newer version of blender go to the folder where you installed it and launch it), then open your blend file from the blender software.