I'm not sure about MX, but for MG you can find it on local satus page > configure.
Configure section contains options for modifying bearer settings such as APN, PIN, and authentication. The ICCID of the SIM card and IMEI of the of the MG cellular gateway can also be found in this section as well. Safe Mode portion allows you to reconfigure port 1 into a WAN role for troubleshooting. To toggle the port 1 from default operating mode into "safe mode" on the MG, check the box to Enable Safe Mode and save.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
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