The keyboard fits 2018 iPad (6th generation), 2017 iPad (5th generation) and iPad Air 1 only!
You can check the model number on the back cover of your iPad.
Compatible with these models below.
2018iPad (6th generation) Model number: A1893, A1954
2017iPad (5th generation) Model number: A1822, A1823
iPad Air1 Model number: A1474, A1475, A1476
Not Compatible with these models below!!!
iPad Air 2 Model number: A1566, A1567
iPad Pro 9.7-inch Model number: A1673, A1674, A1675