The existence of Pluto wasn’t known to the Sumerians. They were similarly ignorant of Neptune and Uranus. If it were chronicled many times in sculpture and in cuneiform, it would have been remarked on by actual scholars of cuneiform and Sumerian, rather than by Zecharia Sitchin. The fact is, it doesn’t occur even once.
Keep on ignoring the evidence. It’s right there in front of your eyes, but don’t believe them. If you are going to knock someone’s work, you might want to actually read it first.