After you set up a Cron Job in hPanel, you will see it at the List of Cron Jobs section. To view the result, simply wait for the Cron Job to be executed (based on the schedule which you set) and click on View Output:
What to do if the output is empty?
If your Job's output is empty, most likely, the command you run doesn't imply an output. For example, line
>/dev/null 2>&1 in the Cron Job is meant exactly for hiding output, and if you remove it, you'll see the output normally.
As one of the solutions, you can add a task to send some simple text phrase when the cron job is executed, f.e. by adding these lines to your PHP script:
echo "hello world\n";
The result will look like this: