@luizfarah Password manager is that page in Settings when you click on "Passwords". Or type

opera://password-manager/passwords

in the address bar and press Enter.

When in the password manager, click on Settings in the left column to see the import and export options.

Apparently they redesigned that section recently, as it used to have the 3 dots you mention, but I rarely need to access that page and hadn't noticed the change.