I closely read the update_field() documentation and built a template that pulls the old content into the new fields.
Looked something like this, this is inside the loop:
// switch on "show field keys", see http://www.advancedcustomfields.com/resources/update_field/
$field_key = "field_somethingrandom"; //this is the new field
$post_id = get_the_ID();
// the $address, $latitude, $longitude values come from the old fields
$value = array(
"address" => $address,
"lat" => $latitude,
"lng" => $longitude
);
update_field( $field_key, $value, $post_id );
Be sure to back up your database, this can mess up your data.
