Data From Notes App On My Macbook Pro Have Disappeared. How Do I Recover This?

I used my macbook Pro after 6 months, and was horrified to discover all the things I'd written in Notes has disappeared.

I went into the Library folder. It has three files:
NotesV7.storedata
NotesV7.storedata-shm
NotesV7.storedata-wal

But when I open these in Text Editor all I get is a lot of garbled text.

iCloud hasnt been much help. I do suspect some 6 or 7 months ago I fiddled with some settings on iCloud. Whether that has caused the Notes data to disappear, Im unsure.

Looking for help, since there's quite a lot of valuable info I really need back.

Thanks.