Snippet data not ported from v3.1.1 to 5.1.1

[alastair-mcdonald]

I'm hoping to upgrade from v3.1.1 to 5.1.1 but can't get 5.1.1 to recognise the db.json file and can't find a way in the app to convert db.json to folders and md files in the file system.
How do I get 5.1.1 to recognise all the snippets built up in 3.1.1?
Sticking with 3.1.1 for now.

Luckily I had a backup of the db.json file because it got deleted by the upgrade.

Thanks.