Automatically fill the Path URL

Dear all,
actually, my users are forced to write a Category path. Category is a content type. As Im expecting to have hundreds of categories in the future, I would like to disable this field (for the users) and let the system to fill-in an GUID or other unique ID (number only) automatically.
I have tried to do this with Pathauto, but as Im a newbie in drupal it doesnt worked for me.

Appreciate any help how to do this.

Best, Miro

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