From Nintendo's financial report -
https://www.nintendo.co.jp/ir/pdf/2018/180426e.pdf
For reference, the NES Classic sold in 2.3 million units as of April 2017.
http://time.com/4759594/nes-classic-millions-sales/
Meanwhile, the Super Nintendo Entertainment System: Super NES Classic Edition proved to be a hit in every region, with sales totaling 5.28 million units.
https://www.nintendo.co.jp/ir/pdf/2018/180426e.pdf
For reference, the NES Classic sold in 2.3 million units as of April 2017.
http://time.com/4759594/nes-classic-millions-sales/