Hi Brian,
Generally the best indicator that the screen needs to be replaced would be if the iPad seems to be working in other respects.
For example, does it respond when you plug it in, via a chime or vibration? Does it do anything when you power it on, again like a vibration or a sound? Is it recognized when you plug it into a computer? After it turns on, does it seem like the touch screen responds (I realize this is tricky without a display)?
If you can get it to respond to you like it would with just a blank display, then it strongly indicates the LCD has been damaged and needs to be replaced, and that will most likely get you going again. LCD displays are made of very thin glass and can crack very easily. In addition, there are a large number of flex cable connections bonded to the glass itself, and those can get dislodged as well. Either of those conditions will kill the screen and the only fix is to replace it.
iFixit has a guide giving you step by step directions on how to do that replacement here.
iPad 9 LCD Replacement - iFixit Repair Guide
Assuming you can get it to display some signs of life, then this is your best bet. The good news is that most LCD vendors will let you return the display as long as it hasn't been installed. This is easy with an iPad as all you have to do is plug it in, reconnect the battery and see if it's working. If so, continue on and reassemble it and you're done; otherwise just unplug it and you can then return the LCD for a refund.
Of course, if there are no signs of life, that is a whole different issue and would probably need to be evaluated by a technician to determine the cause. There are, however, a lot of very good technicians who frequent this forum who might be able to help if that's the situation you find yourself in, so check it out and let us know what you find and we can go from there.
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