C:\Users\[Your Username]\Apple\MobileSync\Backup\
By default, iTunes stores iPhone backups in the following location on a Windows PC: where is the iphone backup stored on pc
The exact path depends on your version of Windows: detailed write-up on the topic:
If you downloaded iTunes via the (rather than installing it directly from Apple's website), Windows stores the backup in a different "Virtualized" location. where is the iphone backup stored on pc
Here’s a clear, detailed write-up on the topic: