SIngle/Bulk Modify - match Logon name to E-mail address?

SIngle/Bulk Modify - match Logon name to E-mail address?

I was wondering if anyone knows how to make it where you can modify users in AD to change their UserPrincipalname to match their Logon name? 
Would this require a CSV or is there a way to do it built-in or with template? 

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