Modern Humans (homo sapiens sapiens) first entered the New World over 12,000 years ago, and are referred to as Paleo-Indians, during the ___?

10th millennium BC and no one of these you told!

The Upper Paleolithic (or Upper Palaeolithic, Late Stone Age) is the third and last subdivision of the Paleolithic or Old Stone Age. Very broadly, it dates to between 50,000 and 10,000 years ago (the beginning of the Holocene).

There is an increasing amount of evidence that people have lived in the Americas since long before 12000 years ago. I think 12000 years ago is the upper paleolithic.