Import Updated iTunes Library to older iTunes 12.8.3.1 on macOS High Sierra

I tried to use a newer version of iTunes on Windows to restore an iPhone that isn't supported on the version of iTunes on my Mac running High Sierra. But when I installed it, iTunes doesn't warn you that it will take your music library from the Mac version and update the file format so that it won't run on the older version of iTunes that's running on your Mac.

I've looked at the proposed solution here: Help using newer iTunes library on older … - Apple Community

but it doesn't work because there is no iTunes Library.xml (or iTunes Music Library.xml) to import and thus restore what you had before the unannounced 'upgrade' to the newer iTunes file format.

So, how can I actually convert the newer file format (which is .itl) to the older format and restore my entire music library and artwork, which isn't that big when you consider it's 19 albums and one or two songs for each of them?

Thanks.

Mac mini mid-2012

macOS 10.13.6 High Sierra

16GB RAM, 512GB Hard Drive

iTunes 12.8.3.1