Is the base wood board, Medium Density Fiberboard, or plywood ?
Are the legs on a steel plate that these screws are anchoring to the base ?
you really want a drill press to screw in the nut insert in the picture above using the double nutted bolt or all thread method. Even using a hand power drill will work, but is easy to get off line and tilt the nut insert or tear out the MDF. Just go very slow on rotation while pressing firmly into the MDF.
I’ve seen many using the screws you were provided. They work as long as the cabinet does not get shifted around much as they will tear out after a while.
the insert in your picture has no pull out resistance to speak of and really isn’t suitable. The threaded nut inserts do a much better job of it.