Firefox WMP plugin:

Install the Windows media player plugin for Firefox.

1 Open a new tab and type about:config into the address bar.
2 Click on the button that says "I'll be careful, I promise".
3 In the search bar at the top, type plugins.load
4 That will show you a line which says plugins.load_appdir_plugins - which will be set to false.
5 Highlight that line by right-clicking on it. Select "Toggle" - that will change the setting to true.
6 Close the tab and restart Firefox. Your missing plugin(s) should now be visible and work as before.

Adobe Flash Player:

Install the Adobe flash player

Select the most recent version or the version you want from the section
 Release and content debugger archives and download.

This version : has the two files you need. 

(Released 11/14/2017) Flash Player (403 MB)Flash Player archives

1  Extract the two files from the arcxhive to a temp directory.
2  flashplayer27_0r0_187_winax.msi.
3  flashplayer27_0r0_187_win.msi
4  install each file.  IE 11 requires winax and Firefox uses win