Hello,
Adobe Flash Player installs in Macintosh HD > Library > Internet Plug-Ins, as it is a browser plug-in. It also installs an uninstaller in Macintosh HD > Applications > Utilities. Use the uninstaller if you want to remove it.
Adobe will stop developing/supporting it in 2020. Due to numerous security issues, it is recommended to uninstall and not run it. If you need it to view a particular website, use Google Chrome, as it has a sandboxed version of it built-in which is much safer.
C