With the old eol Windows 7 the most current Firefox you can run is Firefox 115 ESR currently at 115.29.0esr and planned for updates till 115.33.0esr next year unless Mozilla extends updates again. Firefox 116.0 and later requires Windows 10, 11 to run. You can download Firefox 115.29.0esr at https://www.firefox.com/download/all/desktop-esr/ as just pick 32-bit or 64-bit then language then click on the [Download ESR 115]. https://support.mozilla.org/en-US/kb/firefox-users-windows-7-8-and-81-moving-extended-support