What notifications? Firefox browser doesn't ask for subscription it's a free browser.

Why am I getting emails stating my subscription will be renewed. I do not want a paid subscription

The Firefox web browsers for desktop (Windows, macOS, Linux) and mobile versions for iOS/iPadOS and Android does not have any subscription based versions.

Mozilla does have some subscription based apps as in Mozilla VPN and the premium/plus versions of Pocket, Firefox Relay, Mozilla Monitor, MDN Plus.