Authorize.Net AIM/SIM APIs and Simple Checkout Officially Deprecated

From AuthNet's site:

Our legacy Advanced Integration Method (AIM) and Server Integration Method (SIM) APIs, as well as our Simple Checkout option, are now officially deprecated, meaning we will no longer provide any updates to these APIs.

We have a desktop app written in vb years ago which is using AuthNet, how do I determine if this app is using AIM or SIM? Code below:-

Private Sub DoRefund()
    Try

        Authorizer.Add("x_login", ConfigurationManager.AppSettings("AuthNetID").ToString)
        Authorizer.Add("x_tran_key", ConfigurationManager.AppSettings("AuthNetKey").ToString)
        Authorizer.Add("x_type", "CREDIT")
        Authorizer.Add("x_trans_id", HoldTransID)
        Authorizer.Add("x_duplicate_window", "1")

        Dim decTempTotal As Decimal = decTotValue

        If Not Authorizer.AuthorizePayment(HoldCC, HoldExpMo + "/" + HoldExpYr, HoldCCCID, decTotValue.ToString) Then
            ' insert RefundBatchExceptions record.
            ' logging exception
            Exit Sub
        End If

        ListBox1.Items.Add("Refund successful for Card Order/Credit Card: " + HoldCorderID + "/" + HoldCC + " for " + Format(decTotValue, "C"))
        ListBox1.Refresh()

    Catch ex As Exception
        Throw
    End Try
End Sub

with the changes in AuthNet, do I need to change something in this app?

That is the AIM API. You can tell because of two factors:

1. x_login and other x_* fields which typical of AIM and not their newer XML/JSON APIs
2. This code issues a refund which is not available in SIM