How to permit or forbid file type uploads in DW?

the ancient DW  used to have a setting within each site to allow or disallow images like png or pdf uploads.   I can't find it in the current settings. I have an old website that I'm restoring that had previously blocked png uploads (the file has a red bar through it) . I can't find a setting to allow pngs to be uploaded during file transfers.    Please help.