Hi @Williams, Kim (US) ,
Per my understanding, if you have already started the migration, it is not recommended to apply patches during the process. And it will do no harm patching your servers before the process starts. As you have installed SP1, it is always recommended to update your farm to latest version. If you are using a 3rd party migration tool , just contact with the provider for needed instructions. When using the SharePoint migration tool, please follow the official documentation to perform the migration.
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