upgrading to Catalina

The Age of this computer will Govern what newer version of macOS it will Qualify to install. Use About this Mac from the Apple Icon on Desktop - the required Information will be there.

With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install.  For Best results use Safari to commence the download as Others may not work.

Safari will open a redirect and open the Apple Store where the download can commence

• macOS Catalina 10.15 hardware requirements

Make Time Machine Backup  is very useful and can be used to Revert to Previous Working macOS

Notation - Mojave is the Last version to support 32 bit applications / extensions and Drivers. Catalina, Big Sur & Monterey supports only 64 bit and there is no workaround.

Suggest using Go64 to find 32 bit application before attempting the upGrade. Some or many of the Application already installed may required update or upGrades to 64 Bit Versions.

Are there any AntiVirus, Disk Cleaner, Optimizers, Un-installers, etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal  operation of the OS and may even Corrupt the OS requiring a Reinstallation

From a Secure of Operating System standpoint - Catalina ( Released October 7, 2019 ) may get Security Updates for maybe another few months.

Big Sur released November 12, 2020 has a longer period of time for addition Updates and / or Security Updates.

The history of Apple for Support and Security Updates to existing versions of macOS has been, in the past, for 3 years from date of release.

macOS Big Sur 11 hardware requirements

Back up your data and click on Catalina.

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