Looks like you're thinking of getting a yearly subscription 🙂 And that's great — you can get the most out of Premium for a whole year at a significantly discounted price.
Here's how you can resubscribe:
1. Cancel the ongoing subscription in your Google Play Settings.
2. Once the monthly period has expired, use the in-app banners to resubscribe.
Remember that Google Play does not divide the total amount charged for your subscription and charges one lump sum instead.