2004 Toyota Echo Spark plugs?

Engine problem
2004 Toyota Echo 4 cyl Two Wheel Drive Automatic 28.000 miles

Gee the manual wants owners to change plugs every 3 yrs.
Me an old guy removed the plastic housing over the motor, only to find plugs like I NEVER SEEN before, thin tiny things not much thicker than a ball point pen, also they are in a hole some 6' deep.
I have to go out and buy a wrench to do the job.
But I do not know what size it is, (cant get no sample out to take to the tool shop. Can anyone tell me the size of the socket wrench I need?
Why they have to mess with a plug size? When the old size worked greatfor the last 50 yrs?