I forgot to export an important deck before formating my D-drive. Using hard-disk recovery tools, I got back a “collection.anki2 file”.
Every time I import it into Anki, Anki shows a dialog box: “.anki2 files are not designed for importing. If you're trying to restore from a backup, please see the ['Backups' section of the user manual.][2]” 'corrupt-collections' section of the user manual I couldn’t got a clue, after reading the user manual.
Many many thanks