What kind of change are you trying to make?
If you are using templates, and you make a change to the template, it automatically makes that exact change to every network bound to the template. This is the most common method used for when you have lots of identical sites.
https://documentation.meraki.com/General_Administration/Templates_and_Config_Sync/Managing_Multiple_...
Boundless Digital is a well known third party that makes several tools for automations and provisioning.
https://www.boundlessdigital.com/#
You can also search the app market place for third party solutions.
https://apps.meraki.io/en-US/home
You could also write a Python script using the API to make the changes.
https://developer.cisco.com/meraki/api-v1/
Then there are third party configuration management systems like Ansible. Ansible lets you automate a LOT of things, not just Cisco Meraki networks.
https://docs.ansible.com/ansible/latest/collections/cisco/meraki/index.html
There are just so many options. You are spoiled for choice. It's hard to recommend any specific one without knowing more.
