Thanks, John. I realize now my question may be too convoluted to answer without more details. However, I was able to solve some issues by using a couple plugins to convert my old post types and taxonomies.
The final issues remaining are:
How can I update my old Posts to use their existing Featured Images as the value for a new ACF File field I created for all Posts. I have thousands of Posts that already have a Featured Image, now I just need to update the database so those same image attachments are applied to my new ACF File field.
Additionally, the old database had a column for player names (it was a WordPress custom field). I need all those values to now be migrated to my new Player Taxonomy. This is less of an ACF question and more related to updating values in the database.
