I am installing an over the range microwave "velos" by Whirlpool. After placing the "mounting plate" and setting the bottom of the microwave into the hooks and pushing into position, the next step is to thread two bolts from the above cabinet down into the microwave.

The microwave has two holes that are already threaded or have "nuts" set in place inside the microwave. Well I threaded one, no problem. Then I went to thread the other and it simply pulled the "metal" out and ripped it. So here is my question...Can I use a diferent type of screw such as a self tapping screw? Or can I use a sort of toggle bolt to grip inside? It seems the cavity where this screw was going is roomy enough, but I definitely can't get a nut in there or anything like that.

Suggestions?