Problems installing Adobe Flash on computer with windows 10

I am trying to take a test on a website with the preferred browser of Mozilla Firefox.

However a section of the test uses flash  but does not open. I'm having problems downloading flash on this computer it says it will not run.

In addition I've turned off my Windows defender and also uninstalled McAfee antivirusas the customer service person has said that could be a problem causing flash not to install.

Can anyone give me any suggestions on how to download and install Adobe flash player