Can I extend my apple care?

Yes, you can. Apple started offering renewals for AppleCare last fall. When your AppleCare is nearing the end of its time, Apple will email you letting you know you can extend AppleCare on a monthly basis. So, rather than paying a lump sum for X amount of time. You’ll pay month to month to continue coverage, making it easy to opt out should you get rid of your device.

https://checkcoverage.apple.com

Here is a link to Apple's instructions:

https://support.apple.com/en-us/HT210580