Apple retail stores — which will celebrate their 10th anniversary in May — will welcome their one billionth visitor soon, says Apple Chief Financial Officer Peter Oppenheimer.

For the fiscal 2011 second quarter, Apple saw retail revenue of US$3.19 billion compared to the year-ago — a growth of 90%. The stores saw a record 71 million visitors compared to 47 million in the year-ago quarter.

Oppenheimer says Apple will open 42 new stores in fiscal 2011. Three-fourths of those will be outside the US, including a fifth store in China.

The retail stores sold 797,000 Macs, in the fiscal 2011 second quarter, an increase of 32% from 606,000 a year-ago. And he says — and you knew this was coming — half of those Macs were sold to those who have never owned a Mac before.