Tem que saber o ano do MacBook para poder comprar o adaptador correto.
"About MacBook Air SSD interface standard:
1: 2010 and 2011 version MacBook Air SSD is 6+12 pin, only one side have contact, size is 109 mm*24 mm. It's SATA interface.
2: 2012 version MacBook Air SSD is 7+17 pin, size is 109 mm*24 mm. 2012 version MacBook Pro SSD is 7+17 pin, size is 89 mm*33 mm. It's SATA interface.
3: 2013 and 2014 and 2015 version MacBook Air SSD is both side have contact, one side is 16+12 pin, the other side is 11+14 pin, size is 89 mm*24 mm. It's PCIe X4 interface.
4: 2013 and 2014 and 2015 version MacBook Pro SSD is both side have contact, one side is 16+12 pin, the other side is 11+14 pin, size is 89 mm*33 mm. It's PCIe X4 interface."
http://www.ssd-for-mac.com/blog/files/compatible-m2-ssd-macbook.php