If my opponent has 2 gear in base and plays his Porobot, does he count as the 3rd gear to draw 1, or will there already be 3 gear?

No. Porobot needs 3 other gear — he doesn't count himself.

His ability reads "if you control 3 or more other gear, draw 1." With only 2 gears already on your Base, playing him gives you 3 gear total, but only 2 other gear — the condition fails and you draw nothing. You'd need a 3rd gear already in play before playing him (so he'd be the 4th).