Question about ITunes bckup for iPhone

Did you read the link as posted?

Find backups stored on your Mac or PC

To avoid ruining any of your backup files, here's what you should know:

• The Finder and iTunes save backups to a Backup folder. The location of the Backup folder varies by operating system. Though you can copy the Backup folder, you should never move it to a different folder, external drive, or network drive.
• Don't edit, relocate, rename, or extract content from your backup files. For example, to restore from a relocated backup file, you need to move the backup file back to where it was in the Backup folder or the file won't work. Backups serve as a safe copy of almost all of your device's data and settings. So while you might be able to view or access a backup file's contents, the contents usually aren't stored in a format that you can read.

Search for the backup folder on your Mac

To find a list of your backups:

1. Click the magnifier  in the menu bar.
2. Type or copy and paste this: ~/Library/Application Support/MobileSync/Backup/
3. Select the Backup folder under Folders.

Find a specific backup

On a Mac with macOS Catalina or later:

1. Open the Finder. Click your device.
2. Under the General tab, click Manage Backups to see a list of your backups. From here, right-click on the backup that you want, then choose Show in Finder, or select Delete or Archive.
3. 
4. 
   
5. Click OK when you're finished.

but I just realize iTunes is no longer supported.

What do you mean?

See this Apple article: Locate backups of your iPhone, iPad, and iPod touch

Locate backups of your iPhone, iPad, and iPod touch - Apple Support

my only concern is I might accidentally delete that folder while cleaning my Mac storage . . .

Oops . . . that could be.

You could still try to search in iCloud.

See that link as posted, and scroll to -> Find and manage backups stored in iCloud

If you use Time Machine you can try to search, but that will be a real search. Search from 4 years ago until you cleaned your Mac.

Try this:

Search for the backup folder on your Mac

To find a list of your backups:

1. Click the magnifier  in the menu bar.
2. Type or copy and paste this: ~/Library/Application Support/MobileSync/Backup/
3. Select the Backup folder under Folders.

Then you will find the backup: Your Home -> Library -> Application Support -> MobileSync -> Backup

It's now done in the Finder.

(242126)

I back-uped my old iPhone using iTunes 4 years ago in iTunes

A question: do you use the same Apple ID?

If you connect your iPhone to the Mac, you will see your iPhone in Finder (Side bar -> Location).

At the General tab :

You will see 'Restore Phone'

You can make a backup in iCloud or on your Mac.

It seems that there is no backup at all. I don't know how that is.