Création catalogues, doublons, installation complète Lightroom Classic

I am a bad student. I have accumulated for 20 years photos that I had no time to classify, all by changing my computer several times (Mac and PC), by performing backups reinstalled on the new computer.

Total panic today where I would like to bring order with Lightroom Classic CC. Although having checked "Do not import duplicates", I have duplicate photos, even triplicate ... and others whose files are missing.

I kept all the hard drives as and when I changed my computer.

Would anyone see a solution?

Thank you in advance and Merry Christmas everyone! Pierre

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