See the article Locate backups of your iPhone, iPad, and iPod touch - Apple Support
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.
For old iPhone If you can't back up to iCloud - Apple Support
If restore from iCloud backup failed - Apple Support
About missing information after you restore your iPhone, iPad, or iPod touch with iCloud Backup - Apple Support
If you restore iCloud data in old iPhone in that case the data can be transferred to new iPhone Transfer data from your previous iOS or iPadOS device to your new iPhone, iPad, or iPod touch - Apple Support
