Backup your database first.

To convert personal product attributes to the WooCommerce attributes of your site move to the converter tool in the plugin main menu.

Select the custom product attribute that you want to convert.

Then choose the Name for taxonomy attribute and Slug for taxonomy attribute for the attribute that you want to add.

If you specify an existing slug, then new terms will be added to it and it will be attached to the products.

After clicking on the Go button, you will receive a new attribute with its terms in the list of WooCommerce attributes.