Compare and Add data from one worksheet to another in VBA Excel

How can I add rows of data from one worksheet to another after comparing it with each other for existing entries? I have tried doing it, but the only problem is that there are duplicate entries which are being added to it.

For Each Cell1 In Worksheets(1).Range("A1", Worksheets(1).Range("A1").End(xlDown))
        
        For Each Cell3 In Worksheets(3).Range("A1", Worksheets(3).Range("A1").End(xlDown))
    
            If Not Cell1 = Cell3 Then
                Dim LastRow3 As Long
                LastRow3 = Worksheets(3).Range("A1").SpecialCells(xlCellTypeLastCell).Row + 1
                Worksheets(3).Range("A1:C1").Rows(LastRow3).Value = Worksheets(1).Range("A1:C1").Rows(Cell1.Row).Value
                
            Else
                Exit For
            End If
    
        Next Cell3

Next Cell1

Using Find() is easier to manage than using a nested loop:

Sub Test()

    Dim c As Range, f As Range
    Dim ws1, ws3

    Set ws1 = Worksheets(1)
    Set ws3 = Worksheets(3)

    For Each c In ws1.Range(ws1.Range("A1"), ws1.Cells(Rows.Count, 1).End(xlUp)).Cells

        Set f = ws3.Range(ws3.Range("A1"), _
                           ws3.Cells(Rows.Count, 1).End(xlUp)).Find( _
                                      What:=c.Value, lookat:=xlWhole)

        If f Is Nothing Then
            ws3.Cells(Rows.Count, 1).End(xlUp).Offset(1, 0).Resize(1, 3).Value = _
                                                        c.Resize(1, 3).Value
        End If

    Next c

End Sub