Hello, arnab321.
The thick wire with the suction cup at the end is your high voltage rectified output. This is where you will get your (usually) 10kv-40kv out. The thinner red wires are usually for things like focus, which you probably don't want to worry about. As for the horseshoe design of the pins, the pattern is different for various transformers. The only way to really tell which pins are in and which are out would be to experiment. Usually the power input pins are next to each other, and towards one side of the horseshoe. Once you find the right ones, you can find the ground pin by holding the suction cup wire near the others (NOT THE POWER PINS!) and see which one it arcs to most. The ground, in my experience, is generally towards the middle.
I hope this helps!
Der Strom