Adobe flash EOL
I have an older MAC using Safari OS X ElCapitan 10.11.6, I can't find that version on the adobe deinstall list. What happens if I do nothing?
MacBook Pro 15″, OS X 10.11
See if the links in this Adobe article work for you:
https://helpx.adobe.com/flash-player/kb/uninstall-flash-player-mac-os.html#OS_X_10_4_and_later
If you leave Flash installed it is a security risk since vulnerabilities may be discovered which malware may take advantage. You should always uninstall unused software.