I'm relocating the TV mount installed by the previous owner. The mount uses 3 6.5X60mm self tapper pan head screws with Philips drive. （I measured the screw size by myself, so that's the rough number.)

So for the new location, how big the pilot hole I should drill into the stud?  To mount a TV is so far the most risky home DIYs I have ever done. Would like to play safe. :-D