The advice from others about updating via Microsoft Store, without deleting previous version works. I was having an issue with my music library and encountered many issues uninstalling and reinstalling due to 12.13 update (5 hour session and another 3 hour session with apple support).
Another method is to use the Apple Software Updater on Microsoft computer and it should pick up the change.
Due to the fault finding with Apple support I was told to delete app. Many issues going to Microsoft Store in first instance (faulty installs). In the end, from Apple website, I installed linked version 12.10.11 (64 bit). It installs and gives a message 'Itunes library.itl can't be loaded because it was created by a later version'. I then used Apple software updater, which presented the new version 12.13 and Itunes update worked.
On my computer, I right clicked Itunes and 'run as administrator'.