You'll need to upgrade iPad IOS 9.3.5 to 10.0. You can search on "upgrade iPad IOS 9.3.5 to 10.0" and look at the resulting search for info. Or you can go to https://www.youtube.com/watch?time_continue=188&v=S1QTRUYYw-g and watch then read the comments. It appears some iPAD2 and iPAD1 can't update to IOS 10.
The linked YouTube video recommended making a backup on the Cloud (I think?) and then going to General->Software Updates on your iPAD to see if anything shows up.