Your KAYA PRO subscription is managed by your app store, not by KAYA directly. To see when your current subscription period ends and when you'll be charged for renewal, go to the "Subscriptions" section of your app store.
KAYA PRO refunds are not guaranteed once a payment is made, so if you plan to cancel, do it before your renewal date. See "How do I cancel or manage my KAYA PRO subscription" for the steps, and "Can I get a refund for a KAYA purchase" if you've already been charged.