There isn’t any way that I know of to convert other custom field plugins. I don’t know anything about Metabox, what fields their are or how the data is stored. It is going to take understanding these things for each field type that you want to convert from and the ACF field type you want to replace it with.
For simple text based fields it can be as simple as creating an ACF field withe the same field name (meta_key). But this will probably not work for more complicated field types.
