Where can I find a download for Mac OSX Mojave ?? Its not on the App store anymore ??

It is on the App Store, always has been.

Open Safari, Firefox will not work.

How to upgrade to macOS Mojave - Apple Support

Go to Section 4 and click on Get macOS Mojave.

The App Store should say 'Get' or Download'

If the App Store says 'Open' then it is detecting a previous download of the install app

go to the Applications folder locate Install macOS Mojave.app.

Move it to the Trash, empty the Trash.

Restart, click on the link again, the App Store should say ‘Get' or 'Download'.

macOS Mojave can't be searched for in the App Store, but it can still be downloaded.

How to upgrade to macOS Mojave - Apple Support