how do i copy my itunes backup data from an external drive to a windows comouter

Hello,

Copy backups to another location

If you need copies of your backups, you can find the Backup folder and copy the entire folder (not just part of it) to another place, like an external drive or network-storage location.

When you use Time Machine, it automatically copies your Backup folder when you back up the Home folder on your Mac.

More info here:

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

Try the steps here under Part 3: Copy the iTunes backup to your new computer.

How to move your iTunes library to a new computer - Apple Support