I want to know roughly how many music singles need to be sold to get
into the top 20 in the charts. Also how many singles are typically
sold to get to number 1 in the charts.

This is for the US official singles chart.

That is a moving target.  In 80's when Michael Jackson ruled it was in
the millions today it varies from under a million to a few 100,000
thousand.  There are many factors contributing to this, like time of
release and the tabulation windows.  GRUUVE www.gruuve.com is working
on stuff to answer these question.