Am using the cloud hosted version of Azure Devops (Azure DevOps Services).
How can i make a backup of all my repos, boards, artifacts and pipelines?
There is no native tools to achieve this. Microsoft has long article about data protection in regards of Azure DevOps - link here
There is open source tools to backup repositories - link here
If you need something more complete. - there is a paid solution
I'm not related to any of these solutions.