One section or one hundred, each section has 3 headers (used or not).
Code:
Sub ScratchMacro()
'A basic Word macro coded by Greg Maxey, http://gregmaxey.com/word_tips.html, 02/03/2019
Dim lngIndex As Long
Dim oSec As Section
For Each oSec In ActiveDocument.Sections
For lngIndex = 1 To 3
MsgBox oSec.Headers(lngIndex).Range.Text
Next
Next
lbl_Exit:
Exit Sub
End Sub