hlw i am satish sharma i want to learn revers engineering in nx . plz help me
Reverse engineering is learning by doing. Get an object of your choice and start designing it, that's all.
By having the proper measuring instruments you can start by measure a single solid object (cup, comb, Lego block, etc.), sketch it using your CAD software, and then turn in into a model and you just accomplished what is called Reverse Engineering.
best tool to start with in my humble opinion is a pair of 6" dial calipers.
analog or digital will do. How much resolution is really up to how precise you need to be with your parts.
... I would also include a 6" adjustable Protractor together with the 6" Vernier as per Mark.