Change this line from
If Right(c.Value, 1) = 2 Then c.Resize(, 3).Copy Sheets("Sheet3").Cells(Rows.Count, 1).End(xlUp).Offset(1)
to
If Right(c.Value, 1) = 2 Then c.Resize(, 3).Copy Sheets("Sheet2").Cells(Rows.Count, 6).End(xlUp).Offset(1)
to reflect the Sheet (here Sheet2) and Column (Column F = 6)
so the code becomes
Sub Transfer_Ones_And_Twos_One_Sheet()
Dim c As Range
For Each c In Range("A1:A" & Cells(Rows.Count, "A").End(xlUp).Row)
If Right(c.Value, 1) = 1 Then c.Resize(, 3).Copy Sheets("Sheet2").Cells(Rows.Count, 1).End(xlUp).Offset(1) '<---- 1 = Column A
If Right(c.Value, 1) = 2 Then c.Resize(, 3).Copy Sheets("Sheet2").Cells(Rows.Count, 6).End(xlUp).Offset(1) '<---- 6 = Column F
Next c
End Sub