I need to update my IPad to iOS12

Go into Settings > General > Software Update --follow any onscreen instructions

Here is a support article with more information: https://support.apple.com/en-us/HT204204

Please be sure to make a full backup of your iPad before starting any updates.

Are you sure you have an iPad Air?

What is the “A” model number of your iPad?

The “A” model number of your iPad can be found on the lower area of the aluminium back of your iPad in small print letters right underneath the large, bold printed” iPad”.

Update your iPhone, iPad, or iPod touch - Apple Support