Just to follow on from @ww ’s awesome reply - the number of tunnels will depend on your design. Are you looking for full mesh (hub) or site to site (spoke)?
The calculations to work out each can be found in the below document
https://documentation.meraki.com/Architectures_and_Best_Practices/Auto_VPN_Hub_Deployment_Recommenda...
Darren OConnor | doconnor@resalire.co.uk
https://www.linkedin.com/in/darrenoconnor/
I'm not an employee of Cisco/Meraki. My posts are based on Meraki best practice and what has worked for me in the field.