Try:
Sub Demo()
Dim Shp As Shape
With ActiveDocument
  .Range.InsertBefore vbCr
  With .Shapes("Text Box 2")
    .TextFrame.TextRange.InlineShapes(1).Range.Cut
    .Delete
  End With
  .Characters.First.Paste
  Set Shp = .InlineShapes(1).ConvertToShape
  With Shp
    .LockAspectRatio = True
    .Width = CentimetersToPoints(21)
  End With
End With
End Sub
Do note that doing what you've asked for changes the associated Section break from 'next page' to 'continuous. It also gets pushed to the next page. In any event, it's not clear what you want to do with that Section break.