I have a MacBook Pro, a W10 PC and a W11 PC. I am equally proficient with Macs and PCs. Macs use Finder (the File Explorer equivalent) to do backups of iDevices. PCs use iTunes. My W10 PC has the latest iTunes installed although I seldom use it anymore. I did not install iTunes in in W11 PC but it is the same. I used to do backups into the W10 PC but I have migrated my main computing to the MBP and I now do backups with the Mac. Nonetheless I still had 5 backups in the W10 PC, an iPad backup and 4 iPhone backups. I deleted them all as they were old (2021) and I no longer needed them. I politely disagree with Lawrence above, deleting the 5 backups was nearly instant, a few seconds only, and they all disappeared from iTunes and the PC.
If you want to find out where iTunes on a PC stores the iDevices backups do the following:
First note that iTunes backups are hidden files and you will not see them normally on File Explorer.
1) On the Search Icon on the left side of the Taskbar type exactly %appdata% and hit enter
2) The file folder %appdata% will now show up on the left side. Click it once.
3) On the right side double click Roaming.
4) Double click Apple Computer.
5) Double click Mobile Sync.
6) Double click Backup.
I now show an empty folder since I just deleted my old iTunes backups. You however should see the backups that you still have on your PC. Select any of them and right click it, then click on Properties and you will see the size of the backup. Note that you cannot (and should not) delete the backups from File Explorer, go to iTunes > Edit (on the left top menu) > Preferences > Devices and delete them from there.
Enjoy...