When you insert a supported 3G/4G USB modem (dongle) in your Meraki MX USB port, it you display it's status on Security & SD-WAN | Appliance Status
There is no much else you can do. You can't manage anything related to your dongle like signal status or IP assignment. The only thing you can assign is a Bandwidth limit
So, if you are gonna use a USB dongle, you should pre-configure it with a private IP address from your local subnet, like 192.168.0.100. This way, you can still manage the internal web portal your modem probably has and check things like signal status or SMS.
Algo, your Dongle connection should be bridged, with NAT, firewalling and it's onboard WIFI DISABLED.
