How to provide detailed listing of /tmp directory
As your ls -l /tmp shows /tmp is a symbolic link to private/tmp

So what you want is to replace tmp by what it is linked to e.g.

ls -l /private/tmp


or let ls do it for you using the -H option

ls -lH /tmp


man ls says


  -H      Symbolic links on the command line are followed.  This option is
               assumed if none of the -F, -d, or -l options are specified.


which explains whey ls with no options does show the contents of the directory that is linked to.