When you install Carrara 18.104.22.168,.. it will detect the previous installation of C8, and ask if you want to remove it,. if you say yes,. it will then uninstall the previous version, before it installs the new one.
If you already have C8 pro installed,... then the update to C22.214.171.124, will install into that same folder, after it’s removed the older version.
If you’re installing C8 for the first time, It will create a new folder inside your Daz Folder in Program Files, ..or program files (x86)
The 8.5 beta version should also be installed into a New folder,. so that it’s separate from your C8