Paste range into only blank cells

Maybe:

Sub scrabtree23()
Dim i As Long, y As Long
With Sheets("Sheet2")
    For i = 1 To 10
        For y = 1 To 5
            If .Cells(i, y) = "" Then
                .Cells(i, y) = Sheets("Sheet1").Cells(i, y)
            End If
        Next y
    Next i
End With
        
End Sub