Well, Dovecot is the POP3 server, but the autoconfig information is not generated by Dovecot (it is generated by Virtualmin) and the autoconfig contains a pop3 section, so…pop3 is enabled.
But, I basically don’t understand your question.
What does getting mail from POP3 on your server have to do with managing email from GMail? I have no idea what you’re trying to accomplish as the things you’re asking don’t seem to have any relation to your stated goal.
Looks like you can just look in the autoconfig.cgi script in your domain cgi-bin and add port (I think it’d be 995 for SSL POP3, but it’s been decades since I used POP3, so I don’t know off-hand), and authentication would be password-cleartext (which is why you need to use SSL).
It is not at all apparent to me why this wouldn’t have been added automatically.
But, still, I have no idea why you’re asking about this with regard to GMail. The premise of the question has me completely baffled.