I am planning to convert all categories into tags but I have ACF data connected to the categories. I tried moving 1 category but the ACF data from the category was not moved into the tag ACF data. Is there a way to move category ACF data to the tag ACF data? I have hundreds of category ACF data so it will be really time-consuming if I move them manually. If there’s a way, how can I do it? Thank you.
There is no automated way to move the data from one to the other.
Data is stored in the _termmeta table by the term_id. When you create a new “category” this is a new term with a new term_id even if the name/slug is the same as the original “tag”.
Moving the data would require doing an DB search for all the _termmeta connected to the old term_id and replacing it with the new term_id.
You could, potentially, use the WP create_term hook. In the hook you could search the tags for a matching slug and then copy all of the ACF fields using get_field() and update_field(). Note that you will need to use the field keys to do the update process and NOT the field names.
The only time that ACF data is deleted is when you delete the thing that the data is attached to (post, term, user) and this is done by WP cleaning up the mata data for the deleted thing and not by ACF.