Regex pattern in Word 2013

I have a word document which contains 6 series of numbers (plain text, not numbered style) as following:

1) blah blah blah
2) again blah blah blah
.
.
.
20) something

And this pattern has been repeated six times. How can I used Regex and serialise all numbers before parentheses so that they start with 1 and end up with 120?

You can use VBA - add this to the ThisDocument module:

Public Sub FixNumbers()
    Dim p As Paragraph
    Dim i As Long
    Dim realCount As Long
    realCount = 1
    Set p = Application.ActiveDocument.Paragraphs.First

    'Iterate through paragraphs with Paragraph.Next - using For Each doesn't work and I wouldn't trust indexing since we're making changes
    Do While Not p Is Nothing
        digitCount = 0
        For i = 1 To Len(p.Range.Text)
            'Keep track of how many characters are in the number
            If IsNumeric(Mid(p.Range.Text, i, 1)) Then
                digitCount = digitCount + 1
            Else
                'We check the first non-number character we find to see if it is the list delimiter ")" and we make sure that there were some digits before it
                If Mid(p.Range.Text, i, 1) = ")" And digitCount > 0 Then
                    'If so, we get rid of the original number and put the correct one
                    p.Range.Text = realCount & Right(p.Range.Text, Len(p.Range.Text) - digitCount) 'It's important to note that a side effect of assigning the text is that p is set to p.Next

                    'realCount holds the current "real" line number - everytime we assign a line, we increment it
                    realCount = realCount + 1
                    Exit For
                Else

                    'If not, we skip the line assuming it's not part of the list numbering
                    Set p = p.Next
                    Exit For
                End If
            End If
        Next
    Loop
End Sub

You can run it by clicking anywhere inside of the code and clicking the "play" button in the VBA IDE.