This is one place I disagree. While personally I think she should be in jail the rest of her life. What I think is not important. Trump should tell the DOJ and FBI to stop. What! Am I crazy? No, and here is why.
If Trump was to go after Hillary, that would unite a disheveled democratic party. It would also galvanize the press against him. By being presidential and stepping above the fray he will gain tremendous goodwill. He is seen as benevolent and generous. Not petty and bitter as the press tried to paint him. He proves how wrong they were and are about him. Also, as of today, Hillary and Bill are irrelevant. If Trump makes her the target of an investigation, she is immediately a power player again.
With no power or influence the big money that was paid into their foundation will dry up. They have no influence, unless Trump gives them some. It is best if they just fade away.
The Democratic Party is in a shambles, and fighting internally. An investigation and then prosecution of Hillary will unite the Democratic Party against a single foe.