I upgraded to monterey and now safari is gone and firefox arrived. I want my safari back

Safari has not gone anywhere. Safari is built in to Monterey just as it has been on previous versions of macOS.

Firefox needs to have been manually downloaded to be on your computer. Apple will not install it by default for any reason. So at some point you had to download it, and then forgot about it.

If Safari is not on the dock anymore, look for it in the Applications folder in Finder, or in the Launchpad.

You can drag it back onto the Dock from the Applications folder, or you can open it from the Launchpad, and then right click (control+click or two finger click) on it, then select Options from the menu, and then click on "Keep in dock".

Change the default web browser or email app on Mac - Apple Support may be applicable.

Are you saying Safari is not an option in the Default Browser dropdown?

That should not be possible. There's no way to even delete Safari.

Also, is Safari not in the Applications Folder in Finder?