There is no automated migration feature to convert Confluence Server/Data Center pages using the Assets (Insight) macro to the new built-in Assets macro in Confluence Cloud.

https://community.atlassian.com/forums/Jira-Service-Management-articles/Now-available-Showcase-your-Assets-objects-in-Confluence-Cloud/ba-p/2693143

With the introduction of the built-in Assets macro in Confluence Cloud, users can now showcase Jira Service Management (JSM) Cloud Assets objects directly on Confluence Cloud pages. However, during migration from Confluence Server/Data Center to Cloud, pages that use the legacy Assets macro do not automatically convert to the new Cloud macro. Instead, these macros appear as unsupported or unknown in Cloud, requiring manual intervention to update each page.

• There is no automated or supported method to migrate or convert the legacy Assets macro to the new Cloud Assets macro.

• Manual recreation is required for each page, which is time-consuming, especially for customers with a large number of affected pages.

• This gap impacts the usability and completeness of migrated Confluence content and increases migration effort.