Your device needs to meet specific requirements, in order for you to be able to use AirDrop.
1. If you wish to transfer files between a Mac and an iPhone/iPad/iPod touch, your apple products must be:
Mac from 2012 or later (with the exception of Mac Pro from mid-2012), using OS X Yosemite or later;
iPhone/iPad/iPod touch, using iOS 7 or later.
2. To be able to share information between Mac devices, they have to be one of the following:
iMac – from early 2009 or later;
iMac Pro – all models;
Mac Pro – from early 2009 (the model with AirPort Extreme card) or mid 2010;
Mac mini – from mid 2010 or later;
MacBook – from late 2008 or later (with the exception of the white MacBook from late 2008);
MacBook Air – from late 2010 or later;
MacBook Pro – from late 2008 or later (with the exception of the 17-inch MacBook Pro from late 2008).