There are two things to do here. The first is to get iTunes properly installed. The second is to properly restore the iPad.
Before you can install iTunes, you'll need to remove the existing version IN THIS EXACT ORDER:
Use the Control Panel to uninstall iTunes and related software components in the following order:
- Apple Software Update
- Apple Mobile Device Support
- Apple Application Support 32-bit
- Apple Application Support 64-bit
On some systems, iTunes might install two versions of Apple Application Support. This is expected. If both are present, be sure to uninstall both versions.
Don't uninstall these components in a different order, or only uninstall some of them. Doing so might have unintended effects. After you uninstall a component, you might be prompted to restart your computer. Wait to restart your computer until you're finished removing all of the components.
Here's the article describing this: Remove and reinstall iTunes and related software components for Windows 7 and later - Apple Support
If you need help uninstalling these components, follow these steps:
Once you've uninstalled iTunes, download and install the latest version from https://www.apple.com/itunes
Next, restore the iPad:
Connect the iPad to a computer with the latest version of iTunes running. This means to use a genuine Apple Lightning cord and connect the iPad to a USB port on the computer. The computer will have iTunes version 12.5 or later running. You can locate the version number on the computer by clicking on the iTunes menu (top left) and choosing 'about iTunes'. On a Windows computer, you'd choose Help and then About.*
Hold down the power button and the home button:
> keep holding - the screen will go dark
> keep holding - the Apple appears and then disappears
> keep holding - the iTunes logo with the cord on the iPad screen appears.
> let go - Once the iTunes logo is on the screen of the iPad, you can let go of the buttons.
There is a prompt on the computer screen that says there is something wrong with the iPad.
On the computer, select Restore and follow the prompts. This will erase the iPad, and you will lose all of your content and settings.
The iPad will be ready when it says hello on the iPad screen.
*If the iTunes version is older than 12.5, go to http://www.itunes.com and choose the Download button to download the latest version. Install it before starting to restore the iPad.