Missing Apple Pencil battery level widget, 6th gen iPad, Apple Pencil 1

The Battery Widget does not need to be downloaded. Its built in.

You can get it when swiping all the way to the left to the Widget panel and tap on edit to add it.

click here ➜ Add, edit, and remove widgets on iPad - Apple Support

What is not there?

The Battery Widget should be able to be added from the Widgets panel, and should show the Pencil's Battery percentage. (different from Battery health).

Add a widget to your Home Screen

1. Go to the Home Screen page where you want to add the widget, then touch and hold the Home Screen background until the apps begin to jiggle.
2. Tap at the top of the screen to open the widget gallery.
3. Scroll or search to find the widget you want (Battery), tap it, then swipe left and right through the size options.
4. The different sizes display different information.
5. When you see the size you want, tap Add Widget.
6. While the apps are still jiggling, move the widget where you want it on the screen, then tap Done.

The Battery widget is not in Settings. That's just the Battery settings page.

Please read and follow the steps in the link I provided above carefully. You are looking in an entirely wrong location.

Add a widget to your Home Screen

1. Go to the Home Screen page where you want to add the widget, then touch and hold the Home Screen background until the apps begin to jiggle.
2. Tap at the top of the screen to open the widget gallery.
3. Scroll or search to find the widget you want (Battery), tap it, then swipe left and right through the size options.
4. The different sizes display different information.
5. When you see the size you want, tap Add Widget.
6. While the apps are still jiggling, move the widget where you want it on the screen, then tap Done.