So here let's first find the amount of children every santa, in total, sees in one day. So if there are 400 santas, and each sees 125 children, you can just multiply 400 by 125 to see how many children all the Santas see in one day.
400 * 125 = 50,000
Now, since there are 30 days which all the santas see 50,000 children, you can then multiply 30 by the 50,000 children to get how many children are seen by Macy's Santas in a month.
30 * 50,000 = 1,500,000
So 1,500,000 children are seen by Macy's Santas.
