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Go to the home page of the site collection for which you want to activate the Site Policy feature.
Go to Settings , Site Settings.
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Under Site Collection Administration, choose Site Collection Features.
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Scroll to Site Policy. On the right side, if you don't see Active, choose Activate

2)Enabling barcodes in SharePoint
list settings->Information management policy settings->Item->Enable barcodes

After you turn on this feather, when you create a new item, the list will generate a barcode for that item.
Just like this:

(Do not forget to show these two system generated columns: Barcode Value, Barcode)
Best regards,