You would have to write a script. In the portal you can go "Help/API Docs".
Here is the section from the manual with the request to update a devices address.
HTTP REQUEST
PUT /networks/[networkId]/devices/[serial]
PARAMETERS
SAMPLE REQUEST
curl -L -H 'X-Cisco-Meraki-API-Key: <key>' -X PUT -H 'Content-Type: application/json' --data-binary '{"name":"Your AP", "lat":37.4180951010362, "lng":-122.098531723022, "serial":"Q2XX-XXXX-XXXX", "mac":"00:11:22:33:44:55:66", "tags":" recently-added "}' 'https:
SAMPLE RESPONSE
Successful HTTP Status: 200
{
"name":"Your AP",
"tags":" recently-added ",
"lat":37.4180951010362,
"lng":-122.098531723022,
"serial":"Q2XX-XXXX-XXXX",
"mac":"00:11:22:33:44:55:66",
"model":"MR34",
"address":"1600 Pennsylvania Ave",
"moveMapMarker": true,
"lanIp":"1.2.3.4"
}