Mail in my inbox (iCloud). keeps getting deleted....How do I prevent that?

See the article Change Mailbox Behaviours preferences in Mail on Mac - Apple Support 

Even you keep the settings for one month , its depends upon your service to erase the mails from trash , if the mails are important in future archive them or create a folder in on my Mac section and drag and drop mails from trash in it or do the settings as per screen shot ( archive deleted messages should be check marked ) .

Okay...

I'm using the latest version of Monterey but my Mailbox Behaviors tab does not look like this; it does not include "Bin"; not sure why.

I guess I'm going to have to accept the good with the bad and the mysteries of why things are the way they are.

I'm confused...I use Mail on Mac and Apple iCloud as my account service, so I am mystified that the choices they provide are not clearly explained. It should be pretty simple. Why offer "Never" as a choice if that really isn't possible? If Apple is going to limit my trash size, then shouldn't it tell me that if it's managing my account? With your explanation, it seems unnecessarily complicated if you're using Apple service with Mail on Mac. If I'm using Apple service, shouldn't I expect that my choices are compatible with that service?

Color me baffled.