On the Mac the preferences are under the Thunderbird menuitem, because it is that way in all other applications on the Mac too…

See also this article.

The question was that I am missing this Menu Item. Why did you answer a question that I did not ask.? Please see original question.

Actually, that was the answer, but here's a little more detail:

You do not have Tools > Options on Mac because Mozilla applications on Mac follow Apple's platform UI guidelines.

If you want Tools > Options on your menu, you can get a Windows system, which follows Microsoft's platform UI guidelines.