No you need a router in between.
The ISP will probably have a private subnet behind their modem or some PPPoE-ish config you'll have to configure on the WAN side of your router. And the ISP will have a route to the /28 they provisioned for you pointing to the WAN side of your router.
Then on the LAN side of your router you will have the /28 subnet where usually the first IP is given to the router's interface and 3 more are used for your HA pair and vIP. So you'll have 11 addresses for various NAT'ed services.
Some other vendors allow you to configure a private IP on your WAN interface and then just use a public range as NAT'ed range to point to your internal services. With Meraki however you need to have an actual interface in the same subnet as your NAT'ed range. Possibly because the Meraki will only support doing ARP replies on behalf of the NAT ranges and not route these internally.