During the research I found below link,
Extracting comments from a PowerPoint presentation using VBA
Below is the solution provided in for thissame type of question.
Sub ConvertComments()
''# Converts new-style comments to old
Dim oSl As Slide
Dim oSlides As Slides
Dim oCom As Comment
Dim oShape As Shape
Open "filename.txt" For Output As 1
Set oSlides = ActivePresentation.Slides
Dim myContext As String
For Each oSl In oSlides
For Each oCom In oSl.Comments
myContext = ""
For ShapeIndex = oCom.Parent.Shapes.Count To 1 Step -1
myContext = myContext & oCom.Parent.Shapes(ShapeIndex).AlternativeText & " "
Next
Write #1, oCom.Author & ";" & myContext & ";" & oCom.Text
Next oCom
Next oSl
Close 1
End Sub
I found that this script not fetching the reply comments in the slides, Its only fetching the main comments from the slides, I also tried to update this solution to get all comments from the slide, bad luck I couldn't find the solution.