searching my old keyword hierarchy

Hello, dear experts,

I used digikam almost 20 years ago and built up a very well thought-out keyword hierarchy. Unfortunately, I haven't used digikam in recent years, but would now like to continue using the keyword hierarchy.

I have some backups of digikam.db from back then. But when I open them with the new installed current version of digikam, the old keywords are not displayed.

Unfortunately, I have not been able to install the SQLite browser, which is supposed to allow you to read data.

Do you have any idea how I can find my old keyword hierarchy? And then import it into the new digikam4.db?

Many thanks, Mike