Unable to load Flash Player to iMac ?

For several recent weeks I have come up against the need for Adobe Flash Player to enter web-sites.  I previously had it operational but it has disappeared and the sites tell me I need to upgrade.

My operating system is ...OSX El Capitan 10.11.6

As my Browser I use Safari Version 10.0.03 (11602.4.8.0.1)

I don't know what version of Flash Player I had or now need.

Every time I go through the download process I get the following......

It starts to download normally but the installation stops at 90%.

The end message says "Installation failed".  Click "Finish"

This leads on to Help and Support/ Installation Problems - Mac OS

I have gone this route many times but no success.  I realise I need to change something but don't know what ....Help