Hello MAAinDC,
Sorry to hear that your iPhone's screen is cracked and can'y use it to erase the content. That is still something that can be done with a few simple steps.
Start with putting your iPhone into recovery mode and then use iTunes to restore it. To do that, take a look at the steps quoted below to get you sorted out. You will need to do a force restart to get you started.
If you can't update or restore your iPhone, iPad, or iPod touch
https://support.apple.com/en-us/HT201263
To put your device into recovery mode, follow these steps:
- Turn off your device and leave it off.
- Plug in your device's USB cable to a computer with iTunes.
- Hold down the Home button on your device as you connect the USB cable. Keep holding down the Home button until you see the Connect to iTunes screen.
- When you see this screen, release the Home button. If you don't see this screen, try steps 1 through 3 again.
When your device is connected, iTunes will open. You'll see a message saying that iTunes has detected an iPhone, iPad, or iPod touch in recovery mode.
Take care