SOLVED Updating to Catalina

[ColinBird]

I have an iMac, late 2013 model, that is currently running High Sierra, version 10.13.6. I wanted to update to Mojave (which I'm familiar with on my MacBook) but have been unable to find a download. Wherever I go, I end up with a pointer to Catalina. So ... will I be OK to go straight from High Sierra to Catalina, and are there any points I need to be aware of. I did a SuperDuper! backup yesterday.
A couple of supplementary questions:
According to support.apple.com, there is an option to "Automatically keep my Mac up to date", but it's not visible in my System Preferences. Why?
Is SuperDuper! still preferred over Time Machine?
Thanks - Colin

 

[Lufbrarunner]

If you upgrade to Catalina you need to check if you have any 32bit apps, as they will not work beyond Mojave.
I use both Super Duper and Time Machine for my backups (Belt & braces approach )

 

[Cory Cooper]

Hello,

You could try this to go to Mojave: Upgrade to macOS Mojave

C

 

[ColinBird]

Many thanks, Cory,
I'm running Mojave now and am very grateful for your advice.
My own attempts to find a Mojave upgrade always led me to Catalina, which I didn't really want, owing to the 64-bit issue (thanks Lufbrarunner)
Cheers - Colin