how to find zero errors in vernier callipers,please tell me the answer

Zero of the Vernier Calipers can be found by first taking the Vernier Calipers and moving the movable jaw towards the fixed jaw till they come to close contact .Then make the reading of that which we call as zero error ,continue this process for about 3 to 4 times and take the average of that readings ,this is called “Mean Zero Error“ .

                                                     While making a reading of an object

Correct Reading = Reading of the object – Mean Zero Error.

 

One more point in the question you wrote “Vernier Callipers “ but it is “Vernier Calipers”.