Balu - Please do not post the same question in multiple places... I see the same thing posted here :
http://www.rcindia.org/radios-and-receivers/fly-sky-fs-th9x-9ch-radio/msg38692/#msg38692 . This is the second time we are seeing duplicate posts, kindly note this for future
Always remember that people will see anything you post, regardless of where you post it. Whether they respond or not depends on whether they know the answer, whether they have time to respond at this moment etc. It looks like you posted it in multiple places without waiting for even an hour !
The answer to your question is already here. Just searching for "3500kv prop size" got me multiple threads on this, like :
http://www.rcindia.org/rc-general-topics/working-of-motors-what-is-the-significance-of-kv-to-prop-size/http://www.rcindia.org/electric-power/what-to-buy-outrunner/In short, a 3500kv motor may take utmost a 6x3 prop safely (in normal case). Even that that may be borderline/risky. These high KV motors are used for smaller props spinning at high rpms, typically 4.75 x 4.75 etc props are used on these motors.
To spin a 9x6 prop, you need an appropriate low kv motor.