CiviVolunteer will not install or uninstall
Go to the extensions page (Administer &gt; System Settings &gt; Extensions) then click the arrow/triangle next to the extension name to expand the section.  That will show Local path where the extension files are.

Just removing the files won't remove the leftover bits of the extension from the database.  If it is partially installed but doesn't offer the option to uninstall then things are more awkward.  If you have command line access you could try cv ext:uninstall ....  Failing that you need to look at the install script in the extension, figure out what it adds to the db then manually remove those things.