I am currently using Mac OS Mojave 10.14.6 and while updating to Mac OS Catalina while installing is shows the error 'You must be running macOS Catalina 10.15 or later to install into this volume.
How do I install the update on my Mac now?
MacBook Air 13″, macOS 10.13
How to update the software on your Mac - Apple Support
You may well have to go to the App Store to obtain MacOS Catalina.
I have already downloaded the update the problem arises during installation
by looks of things, you downloaded just the combo update. you need to download the entire macOS Catalina.
How to upgrade to macOS Catalina
Unable to install Mac OS Catalina
