The last supported version for the affected operating systems will be Firefox version 115, which is planned for the beginning of July 2023.
For a short time, an ESR (Extended Support Release) or LTS (Long-term Support) version will be available for these users before support finally ends in 2024.
https://www.pcworld.com/article/1940069/mozilla-ends-firefox-support-for-windows-7-8-old-macs.html?