Passwords are not kept in a .pcv file but in :

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data
• logins.json (passwords) and key4.db (58+) or key3.db (57 and older) (decryption key) for Passwords saved in the Password Manager
• if you only have key3.db then make sure to remove an existing key4.db

Note that a .pcv file is a ZIP archive, so you can open this archive with a suitable archive manager and see if it has logins.json and key4.db used in current Firefox releases to store the passwords.

If the backup you used only has logins.json and key3.db used in older Firefox versions then you need to remove an existing key4.db file to make Firefox use key3.db. This file stores the encryption key that is used to decrypt the passwords stored in logins.json.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Thank you both very much!! )))