Hello SaurabhAgrawal,
Thanks for posting in the Apple Support Communities forum. We understand you'd like to use the flash feature on your iPad, but aren't seeing the option to do so. Usually this would be found in the camera app or you can test if the feature is available by swiping down the control center and enabling the flash light feature, if available.
According to the iPad Air (4th generation) - Technical Specifications, there's only a flash available for the front-facing FaceTime HD camera. If that flash on your iPad isn't working, use the following steps:
Quit and reopen an app on iPad
Then Restart your iPad and try again, taking a picture with the front-facing camera.
Have a great week!