You would first need to know where the ACF field is saved. This would depend if the group is a post or a term or something else. You will need the ID of the post or the term you would need to query the correct table to get this informsion. Using this you would then need to query either the “_postmeta” or the “_term_meta” table using the ID and the ACF field name.
I do not know how you would do this outside of WP.