MacOS updating

The Go64 is Trusted and suggested by more Senior Contributors on these Forums It is used to identify the 32 bit applications and prepare to upgrade or replace the 32 Bit Application to a 64 Bit application.

Mojave is the last version of macOS that supports any 32 bit anything.

As for what version to upgrade too - would suggest High Sierra and once that is achieved , one can move up the chain to whatever version the computer qualifies for.

The Apple Store on Sierra will no longer show the versions above like High Sierra, Mojave , Catalina, Big Sur or , Monterey.

This is because, at the time High Sierra may have been offered as an upGrade - the user ( you ) chose not to upGrade at that time. Nothing wrong with that, it just makes the upGrade process a bit more complication but doable.

If intending to upgrade to Mojave, Catalina, Big Sur or Monterey - suggesting to upgrade to High Sierra first. This will better position the computer to convert to the new APFS format and install any BOOT ROMs required to work with the filing system. Each of the already mentioned newer versions Mojave etc. need to work on the APFS system

To achieve the High Sierra upgrade - your choice see below >>

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.

As Added information Tips Big Sir Upgrade

As Added information Tips Monterey Upgrade 

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

Often time it mean the Full Installer of whoever upGrade version of macOS is Corrupted.

There are factors:

1 - Like poor Wifi connection

2 - Slow wifi connection

3 - Too many other people downloading at the same time and Apple Severs are overloaded

4 - Software on the computer interfering with the download process including AntiVirus Software

5 - Running behind a VPN which may increase Packet losses

6 - If via wifi too many Other devices using the wifi at the same time reducing the Bandwidth to your computer. 

7 - Best Results are via Ethernet Cable to Router

If the Firewall is on the Router, personally, would. tun it off.

Want the Maximum Bandwidth and nothing interfering in the download process.

Out of interest - which upGrade is being considered ?

Welcome and thank you too.

Do come back to the ASC forums if / or when addition assistance is needed. Or just to hangout and view other persons questions and possible solutions.