Hi,
as you correctly noticed, the UI of the alert creation got updated and does no longer align with the one presented on the screenshot. The Evaluated based on section has now moved under the Advanced drop down field - you can open it and configure it right there.
Please make sure, that the frequency of evaluation is less than or equal to the evaluation period (open the advanced setting for this). Setting those to numbers to be equal should fit in your case.
Regards,
Andy