Trump is, of course, a dolt.
I mean, hell, just the basic techniques that Wired describes are things that I know to do to search through a bunch of emails for stuff. That's completely aside from what sort of advanced data algorithms and processing systems the FBI (like their other intelligence cohorts) have to apply to the problem.
Of course, I have no idea if Donald Trump really believes this, or if he's just blowing smoke for the sake of the campaign. Either way, he's wrong.
Yes, Donald Trump, the FBI Can Vet 650,000 Emails in Eight Days
But Trump knows more about computers than Snowden does.