can some one suggest me good frame and motors which is suitable of lifting 3kg on hexa using flight controller px4

Tarot 680 and Tiger 400kv motors.
Or rctimer 350kv motors + rctimer s800 clone frame with landing gear

What you are planning to lift nikhil?

I am planning to lift an test apparatus to take readings in different places and do research on tree canopies which are not easy to be reached easily

thanks rahul how much flytime i can expect with it ?

10min+ plus I suppose.

If you need the largest flight time, look no more than 5010 360kv with 16" props from rctimer with 6S.
But you will have to build your own frame.

If you are restricted to 4S, use the 3608 720kv motors with 5S and 11" props.