How do I get the passwords for the older Might and Magic games 1 - 5 ?

I was going to make a stupid joke about them automatically being mailed to you once you clock over 1000 hours in the games, then I looked at your profile and that joke suddenly became far less funny than I'd originally thought it might be.

I'm not sure, but maybe this post will help you:

https://www.gog.com/forum/might_and_magic_series/world_of_xeen_leaving_vertigo/post6

If you're seeking serial numbers to games sold by GOG, some are not freely given. You would have to contact support. Albeit dated, this page might prove useful.

I'd assume passwords would be similar to NES games which was an offline save-system. Another World/Out of this world also employed passwords.