I've never tried it and don't want to need to, but you can try these two APIs.
GET /organizations/{organizationId}/floorPlans → retrieves all floor plans.
GET /networks/{networkId}/devices → retrieves device info, including location.
https://developer.cisco.com/meraki/api-v1/get-organization-floor-plans-auto-locate-devices/
You can combine these to build a structured export (JSON or CSV) for your vendor.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.