https://support.mozilla.org/pt-BR/questions/1253828

Enable Dev Tools

Open up a new tab, go to about:config. Search for “devtools.chrome.enabled” and set to true

Now open up the Browser Console with “Ctrl + Shift + J” and past in the following

try {
  signons = Services.logins.getAllLogins();
  var csv = '"Site","Username","Password"';
  for (var i=0; i<signons.length; i++){
    csv += '\n';
    csv += signons[i].httpRealm ? 
      ('"' + signons[i].hostname + ' (' + signons[i].httpRealm + ')","') : 
      '"' + signons[i].hostname + '","';
    csv += signons[i].username + '","' + signons[i].password + '"';
  }
  console.log(csv);
} catch (err) {
  console.log('Problem reading or outputting logins: '+err);
}

Hit enter to run the command and return all the saved logins. You can copy and paste them, or export to file.