Moving one TempdB on 3 instance server
Tempdb files are recreated each time the sql server starts.  After you change their location using ALTER DATABASE, you can verify your change by checking the dmv tempdb.sys.database_files.  (not sys.master_files, which won't be updated until sql restarts).  

Sql will create new files for tempdb, and will leave the old ones on disk, so you should delete them.