I did quite a bit of work with licence plate recognition in the distant past. I used Plate Recognizer because of their native Meraki support.
https://platerecognizer.com/camera-integrations/meraki/
You then use their API, and they call your web hook with the number plate seen.
I'm not aware of any "off the shelf" solutions - but that is half the problem solved above. Make sure you use a camera that supports recognising cars. I would take a look at the MV73X.
You could also search the Meraki App Marketplace for existing solutions.
https://apps.meraki.io/en-US/home