They are stored in a file called signons.sqlite inside the profile folder. The key3.db file in the profile folder contains the key used to encrypt/decrypt the passwords. Those 2 files need to be kept together. For details of how to find the profile folder see https://support.mozilla.com/kb/Profiles

Too detailed. I just want them to turn on and work. They are not in the same place as before I updated.

The options for passwords are in the same place in the options dialog as they were in Firefox 3.6.

1. Click the orange Firefox button and select Options to open the options window
2. Go to the Security panel to access the settings for passwords

If they are not working see https://support.mozilla.com/kb/Remembering+passwords and https://support.mozilla.com/en-US/kb/Username+and+password+not+remembered

Thank-you!