Replacement bolt size for Thermostat outlet 94 Explorer XLT

I was replacing the thermostat and flushing the radiator this weekend
following Dr. Bob's instructions and I misplaced one of the 3 bolts
that go on the thermostat outlet.

Does anyone know the size of the replacement bolt I need? Can someone
look it up in their service manual? I have a 94 Explorer XLT.

BTW, I misplaced it because I removed the thermostat to flush the
radiator -- and only used two bolts to do this -- when I went to
reassemble everything the next day, I couldn't find the third bolt. I
searched everywhere for about 3 hours today but couldn't find it -- I
hope saving a hundred bucks isn't going to cost me a 1500 engine
overhaul if the bolt finds its way into a bad spot. I'm pretty sure I
just misplaced it because I'm always good about retrieving bolts that
drop down. If it fell into the engine, hopefully I would have been
searching for it saturday night. Anyway, I wish I did the flush the
other way -- just opening the radiator drain and putting the hose in
the radiator.

Thanks, Herb