Hello, you can install 52 ESR which supports legacy extensions, and will be supported with security updates until May 2018. You can get it from here: https://www.mozilla.org/en-US/firefox/organizations/all/

if this solved your problem, please mark as solution.

Thanks MkII, I can now see the addons pages, so much fun will had there as I try to find replacements for all my beloved addons which have been disabled by the malodorous perverts wot wrote this new version ! Grrr ! If I can't find satisfactory replacements I'll be orf to Opera ! First I will write down my fave websites ! You don't catch me making the same mistake more than four or five times...

Duplicate, please continue in https://support.mozilla.org/en-US/questions/1184776