Something like this might work for you.
If you have headers in Sheet1 and Sheet2 this can modified.
Also not sure if you wanted B copied from Sheet1 or just A and C, this does A:C
Sub findNA()
Dim r, x, lr1, lr2 As Long
Dim vNA
Dim ws1, ws2 As Worksheet
Set ws1 = Sheets("Sheet1")
Set ws2 = Sheets("Sheet2")
lr1 = ws1.Cells(Rows.Count, 1).End(xlUp).Row
lr2 = ws2.Cells(Rows.Count, 1).End(xlUp).Row
For r = 2 To lr1 ' assuming you have headers in row 1 (make 1 to lr1 if no header)
If ws1.Cells(r, 2).Text = "#N/A" Then
If ws2.Cells(lr2, 1) = "" Then
ws1.Range("A" & r & ":C" & r).Copy ws2.Cells(lr2, 1)
ElseIf ws2.Cells(lr2, 1) <> "" Then ' not needed if headers on sheet2
ws1.Range("A" & r & ":C" & r).Copy ws2.Cells(lr2, 1).Offset(1)
End If
End If
Next r
End Sub