For future reference, I’d like to add a simple solution to get tar working on Windows 10, as I ran into this problem myself with running OJS 3.2.0.2 on XAMPP 7.4.5-0-VC15.
Windows 10 does include tar since build 17063 and therefore you just have to add the escaped path to your config.inc.php. Replace tar = /bin/tar with:
tar = C:\\Windows\\System32\\tar.exe
This worked for me and now I’m able to install plugins from the Plugin Gallery.