The most reliable way to find out which model of iPad you have is to look at the model number on the back of your iPad.

iPad 6

iPad 6 Wi-Fi: Model A1893
iPad 6 Wi-Fi Cellular: Model A1954

iPad Pro 12.9" 2nd Gen

iPad Pro 12.9" 2nd Gen Wi-Fi: Model A1670
iPad Pro 12.9" 2nd Gen Wi-Fi Cellular: Model A1671

iPad Pro 10.5"

iPad Pro 10.5" Wi-Fi: Model A1701
iPad Pro 10.5" Wi-Fi Cellular: Model A1709

iPad 5

iPad 5 Wi-Fi: Model A1822
iPad 5 Wi-Fi Cellular: Model A1823

iPad Pro 9.7"

iPad Pro 9.7" Wi-Fi: Model A1673
iPad Pro 9.7" Wi-Fi Cellular: Model A1674

iPad Pro 12.9"

iPad Pro 12.9" Wi-Fi: Model A1584
iPad Pro 12.9" Wi-Fi Cellular: Model A1652

iPad Mini 4

iPad Mini 4 Wi-Fi: Model A1538
iPad Mini 4 Wi-Fi Cellular: A1550

iPad Mini 3

iPad Mini 3 Wi-Fi: Model A1599
iPad Mini 3 Wi-Fi Cellular: Model A1600
iPad Mini 3 Wi-Fi Cellular Cn: Model A1601

iPad Air 2

iPad Air 2 Wi-Fi: Model A1566
iPad Air 2 Wi-Fi Cellular: Model A1567

iPad Mini 2 Retina

iPad Mini 2 Retina Wi-Fi: Model A1489
iPad Mini 2 Retina Wi-Fi Cellular: A1490
iPad Mini 2 Retina Wi-Fi Cellular Cn: A1491

iPad Air

iPad Air Wi-Fi: Model A1474
iPad Air Wi-Fi Cellular: A1475
iPad Air Wi-Fi Cellular Cn: A1476

iPad 4 with Retina display

iPad 4 Wi-Fi: Model A1458
iPad 4 Wi-Fi Cellular: Model A1459
iPad 4 Wi-Fi Cellular: Model A1460

iPad Mini

iPad Mini Wi-Fi CDMA: Model A1455
iPad Mini Wi-Fi GSM: Model A1454
iPad Mini Wi-Fi: Model A1432

iPad 3

iPad 3 LTE: Models A1430 & A1403
iPad 3 Wi-Fi: Model A1416

iPad 2

iPad 2 Wi-Fi CDMA: Model A1397
iPad 2 Wi-Fi GSM: Model A1396
iPad 2 Wi-Fi: Model A1395

iPad 1 (First Generation)

iPad Wi-Fi: Model A1219
iPad Wi-Fi 3G: Model A1337