How to take a picture that is on Facebook with my new new generation 10 iPad?

By far the easiest method to trigger and save a screenshot is to set-up and use the corner-swipe gesture.

Settings > Multitasking & Gestures >

• Swipe Finger from Corner - set to ON
• Bottom Left Corner > select Screenshot or Quick Note as required
• Bottom Right Corner > select Screenshot or Quick Note as required

Once the corner-swipe gesture has been enabled, you can easily capture a screenshot with just your finger. Simply swipe diagonally from the lower-left or lower-right corner of the screen towards the centre; this will immediately trigger the screenshot.

If you have Apple Pencil, you can similarly trigger a screenshot using a corner-swipe gesture using the Pencil:

Settings > Apple Pencil > [Pencil Gestures] Left | Right Corner Swipe - select Screenshot for one, other or both gestures

The other ways to trigger a screenshot from an iPad are described here:

Take a screenshot on your iPad - Apple Support

Press the top right button and top button on the right side, simultaneously.