Mojave is not available anymore on the app store, where can I find it??

Using exclusively Safari, visit How to get old versions of macOS - Apple Support and verify that your Mac is compatible with the hardware requirements. If so, then follow the Mojave link to its location in the Mac App Store. A full installer will be saved to your /Applications folder as Mojave 10.14.6.

As with any upgrade, you need to verify that your third-party vendors provide application versions compatible with Mojave. Same is true for compatible device drivers for your printer/scanner and other peripheral vendors. Remove any anti-virus or so-called Mac cleaner products, make a final Time Machine backup, and then perform the upgrade.

Use the link for it in the support document you came from.

Or click here-> https://apps.apple.com/us/app/macos-mojave/id1398502828

Do note, you must be using the Safari Browser on a compatible computer or if on an incompatible computer, the Apple ID logged in for the App Store must have downloaded Mojave at some point in the past to get the option to re-download it.