What is your meaning of Teams migration? Do you mean the users and its resource moving from on-premise to online?
What is the meaning of the data? Teams files or chat history?
At present, Microsoft Teams is not provided such migrated teams report to identify if the data is moved. So if you can see teams in target, it seems you could try to check it in each data storage. For example, if you want to know files has been moved, you could go to SharePoint Online to see it. For more details about Teams migration data location, you could refer to this article.
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