how can I update my mac operating system?

Depending on what OS you are running, you can either find system updates in system preferences or the App Store.

To check on System Preferences:

• Click the Apple Logo () on the Menu Bar (top left corner)
• Click "System Preferences"
• Find the Setting "Software Updates"
• There you should see and pending updates and you can continue to update from there.

To check on App Store:

• Open the "App Store"
• In the sidebar, click "Updates"
• Click "Update next to anything the needs to be updates

Good Luck!

Source: Update from app store: https://support.apple.com/en-us/HT202180

Update from System Preferences: https://support.apple.com/en-us/HT201541

llking6 wrote:

I am trying to update my operating system and I am not getting any software update access in the App store.

You will have to verify your tech specs for your exact Mac/year to verify/compare the macOS that is compatible...

The older macOS installer backups on this server:

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

verify you are using the Safari browser to download/initiate the macOS links.