@Nitin_16 Unfortunately, you cannot read the value of created by column in calculated column OR you cannot change the value of created by column using calculated column.
You can change the value of created by column using SharePoint REST API ValidateUpdateListItem endpoint.
Check this example doing the same using Power automate: How to update editor and author fields in SharePoint using Power Automate
Note: You have to use the Author instead of "Editor" (shown in above link) as the internal name of SharePoint created by column is "Author".
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