Hard resetting

You can't. It would be like asking how to start your car if the ignition key is broken. You need to get your iPad serviced. But be advised, Apple doesn't repair iPad. They offer out of warranty replacement for about 60% of the price of the iPad when new. If you have an older iPad, it may be smarter to invest in a newer device.

If the physical Home Button is broken, you’re not be able force the iPad into recovery mode or a forced-restart.