You can identify the model of your device by referring to the number printed on the back of the device 

Model: Model #

iPad 2: A1395, A1396, A1397

iPad 3: A1416, A1430, A1403

iPad 4: A1458, A1459, A1460

iPad Air: A1474, A1475

iPad Air 2: A1566, A1567

iPad Mini: A1432, A1454, A1455

iPad Mini 2: A1489, A1490

iPad Mini 3: A1599, A1600

iPad Mini 4: A1538, A1550

iPad Pro 12.9": A1584, A1652

iPad Pro 9.7": A1673, A1674, A1675