Did you mean 2018? You have until April 15th to file an extension for 2018.
But if you just bought the 2016 TurboTax software to file either an original 2016 AZ return or to amend your previously filed 2016 AZ return, in neither case do you need to file an extension.
The time to file an extension for AZ for 2016 ended in April 2017. Just print and mail the return when you are done with it.