uSync Sync-Pack files (with the .uSync extension) are simply ZIP files and can be viewed in any ZIP viewer, including the one built into Windows.
One option is to rename your Sync-Pack to have a .zip extension and then open it as you would any compressed folder.
The other option, however, which is very useful if you’re looking inside uSync files more often, is to let Windows know that the .uSync file is a ZIP file and to treat it as such.
There’s no point-and-click setting for this like there is for associating a filetype with a program because we’re doing something subtly different: telling Windows this file is a ZIP file.
All you need to do, though, is open a command prompt as administrator and run: