Replace file extension

ls C:\Temp\Tesingname\*.* | ? { !$_.PSIsContainer   -and   $_.extension -eq '.txt' } |   ren -NewName { "$($_.BaseName)_$(get-date -format "yyyyMMdd_HHmmss")$($_.extension) "  }  

ls C:\Temp\Tesingname\*.* | ? { !$_.PSIsContainer   -and   $_.extension -eq '.log' } |   ren -NewName { "$($_.BaseName)_$(get-date -format "HHmmss")$($_.extension) "  }