Where do I get install code for Mac OS Mojave?

Where do you see that an 'install code' is required?

• How to get old versions of macOS - Apple Support

https://support.apple.com/en-us/HT211683

• How to create a bootable installer for macOS - Apple Support

https://support.apple.com/en-us/HT201372

There are processes, procedures, & instructions

..to get and use the downloadable installers..

PS: Several useful links on topic of formatting Mac storage HDD/SSD

& 'install/reinstall/recovery' -- covered in thread, with few duplicates:

• Formatted Hard Disk - Apple Community (answered 23 Dec 2020*)

https://discussions.apple.com/thread/252210960?answerId=254199712022#254199712022

*One may consider linked "Codes" in "Create a Bootable Installer"

as there are some copy-paste items there for each of recent macOS.

["There had been a few different ways to create bootable installers, with code for each version.

One of latest articles I'd seen, covers currently supported versions; however subject to change.

..The 'createinstallmedia' command in Terminal shows a different code for each major macOS."]

..Although I'd written that a little while ago, had read of it several years ago..

..Good luck & happy computing.!

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