Generally, at the right front corner, just follow the 1/4'" diameter black wire to the cap concealing it. If this a newer engine, it is probably an RC-12YC or equivalent. Remove the cap carefully as it will often tend to stick to the plug.
.03
0.030"
.30 gap for craftsman 3.5
Rj19lm or j19lm
1/2 an inch
.030
Spark plug gap should be .025 http://store.chainsawr.com/
Not sure how to answer your question with the right answer. However, lawn mower spark plugs come in three sizes: 5/8, 3/4 and 13/16.
.030"
If it's the metal bar near the spark plug that you push towards the plug to kill it, all it does is ground out the plug, making it not spark. That bar is connected to the frame of the mower ie grounded which in turn grounds out the plug and wire
.030"
The Briggs and Stratton part number for a standard spark plug is 496018S. You can either buy this exact plug or call around to local lawn mower shops or auto parts providers (NAPA, O'reilly's...) and get them to cross reference the part number to see what other plugs will work.