Missing playlists after iTunes update?!

I updated iTunes this weekend (22nd July 2017). Everything seemed to work as planned at the time. However, all of the Playlists I'd created in my iTunes library have disappeared - that's many playlists created over many years.

I realise this isn't uncommon (which is worrying in itself - why does it happen?) and I've had a look on some of the previous threads and questions/suggestions on the Support pages, but most of them seem quite complicated. However, I'm trying to work my way through some of the information and advice provided.

A further query and confusion I've got is that when I search for Previous iTunes Libraries I can't find one with a date more recent than some time in 2015 - I was expecting to find a saved Library from the date of the iTunes upgrade? (or at least from an update more recently than 2015).

My iPod Classic contains all of the playlists, but I can't find anyway to transfer that list back to iTunes (transferring purchases doesn't work).

Any help, with very simple explanations, or new ideas, would be very helpful please.

I really don't want to have to start recreating Playlists from scratch!