importing data from text file

Sub a()
Call ReadTextFile
LR = Cells(Rows.Count, "J").End(xlUp).Row
n = 1
For r = 1 To LR Step 16
  Range("A" & n) = n
  Range("B" & n) = Range("j" & r + 3)
  Range("C" & n) = Range("j" & r + 6)
  Range("D" & n) = Range("j" & r + 9)
  Range("E" & n) = Range("j" & r + 12)
  n = n + 1
Next
Columns("j").ClearContents
End Sub
Sub ReadTextFile()
folderPath = "C:\Users\user\Desktop\" ' <<<< to be changed
Filename = "sample.txt"
sn = CreateObject("scripting.filesystemobject").opentextfile(folderPath & Filename).readall
sp = Split(sn, vbCrLf)
n = UBound(sp)
For j = 0 To n
  Range("J" & j + 1).Value = sp(j)
Next
 
End Sub

Here's my version. Not nearly as compact as patel45.

Sub ImportData()
Dim WS As Worksheet
Dim aCol As Long
Dim NextRow As Long
Dim FileToOpen As String
Dim TextLine As String
Dim Temp As Variant

FileToOpen = Application.GetOpenFilename("Text Files (*.txt), *.txt")
Set WS = ActiveSheet
With WS
NextRow = .Cells(.Rows.Count, "A").End(xlUp).Row + 1

If FileToOpen <> "" Then
    Open FileToOpen For Input As #1
    
    Do
    Line Input #1, TextLine
    If InStr(TextLine, "#BEGIN") > 0 Then
        aCol = 1
        Temp = Split(TextLine)
        WS.Cells(NextRow, aCol) = Temp(UBound(Temp))
        
        Do
            Line Input #1, TextLine
            If TextLine Like ("[#]*:") Then
                Line Input #1, TextLine
                aCol = aCol + 1
                WS.Cells(NextRow, aCol) = TextLine
            End If
        Loop Until EOF(1) Or InStr(TextLine, "#END") > 0
    End If
    NextRow = NextRow + 1
    Loop Until EOF(1)
    Close #1
End If
End With

End Sub

not compact but more flexible.