Hi Rahul,
Hope you are doing well !
outside vpn here refers to Site to Site VPN. I am assuming the same.
To block all outside VPN connections on a Meraki network, you need to configure firewall rules within the Meraki dashboard, specifically targeting VPN traffic by protocol and port numbers, effectively denying all incoming connections on those ports; you can access relevant documentation in the Meraki dashboard under "Security & SD-WAN > Configure > Firewall.
But before the above steps permit the connection from known vpn peer on same protocol.
If you are referring to client to site vpn.
https://documentation.meraki.com/MX/Client_VPN/Restricting_Client_VPN_access_using_Layer_3_firewall_...