Need macro to split one column into multiple columns based on _ and spacing

Different method for Sheet1

Perhaps few lines are not converted properly though...

Sub test()
    Dim a, i As Long, ii As Long, b() As String, n As Long, x, temp
    With Range("a1", Range("a" & Rows.Count).End(xlUp)).Resize(, 4)
        a = .Value
        ReDim b(1 To UBound(a, 1), 1 To 5)
        With CreateObject("VBScript.RegExp")
            .Global = True
            On Error Resume Next
            For i = 1 To UBound(a, 1)
                If a(i, 1) <> "" Then
                    .Pattern = "\.pdf"
                    a(i, 1) = .Replace(a(i, 1), "")
                    .Pattern = "00"
                    a(i, 1) = .Replace(a(i, 1), "0")
                    .Pattern = "(.+)(?:[_\-])(\d{1,2})(\d{1,2})(\d{4}|\d{2}) (.*)$"
                    If .test(a(i, 1)) Then
                        b(i, 4) = CDate(.Replace(a(i, 1), "$4/$2/$3"))
                        b(i, 5) = Trim$(.Replace(a(i, 1), "$5"))
                        temp = .Replace(a(i, 1), "$1")
                        .Pattern = "[^_]+"
                        For ii = 0 To .Execute(temp).Count
                            b(i, ii + 1) = .Execute(temp)(ii)
                        Next
                    Else
                        .Pattern = "(.+)(?:[_\-])(\d{1,2})(\d{1,2})(\d{2|\d{4})\d?"
                        If .test(a(i, 1)) Then
                            temp = .Replace(a(i, 1), "$4/$2/$3")
                            b(i, 4) = CDate(.Replace(a(i, 1), "$4/$2/$3"))
                            temp = .Replace(a(i, 1), "$1")
                            .Pattern = "(\d+)[_\-](\D+)[_\-](\d+)"
                            For ii = 1 To 3
                                b(i, ii) = .Replace(temp, "$" & ii)
                            Next
                            b(i, 5) = Trim$(a(i, 2) + a(i, 3) & " " & a(i, 4))
                        End If
                    End If
                    temp = ""
                End If
            Next
        End With
        With .Offset(, .Columns.Count + 2).Resize(, 5)
            .Value = b
            With .Columns(4)
                .NumberFormat = "mmddyyyy"
                .Value = .Value
            End With
        End With
    End With
End Sub