How to change upload destination from private to public?
You could accomplish this by moving the files out of the private directory and into the public directory (make sure the paths stay the same!). Then you would need to update the 'file_managed' table. The 'uri' table will list the files as either private or public. The mySQL would be similar to:

UPDATE file_managed SET uri = REPLACE(uri, 'private://', 'public://') where instr(uri, 'private') &gt; 0;


NOTE Please make sure to test this on a dev site before doing in production.