What device do you have? You should have a Play Store app in your app drawer. It the device is old enough the apps may not update. How are you getting informed that you have appts that need to update?
Welcome to Android Central! Or if you have a device that's not certified for Google Play (like recent Huawei devices), then you don't have access to the Play Store.
Welcome to Android Central! Is it telling you that you need to update the Play Store? Open the Play Store app, then tap Menu>Settings>Play Store Version. If there's an update available, it should prompt you to tap to proceed with the update.