VB.NET debug code

I am in the process of migrating a VB6 app to VB.NET. A problem that I am coming across is the following error: "Name 'LoadResString' is not declared"
The code this is located in:
    Sub LoadResStrings(ByVal frm As Form)
        On Error Resume Next

        Dim ctl As System.Windows.Forms.Control
        Dim obj As Object
        Dim fnt As Object
        Dim sCtlType As String
        Dim nVal As Short

        'set the form's caption
        frm.Text = LoadResString(CInt(frm.Tag))
...
...

I have searched the converted code and the original code and there is no mention of a function or routine called "LoadResString". The original VB6 code compiles and runs just fine, without errors or problems, not sure what is going here, could this be referencing some external file with the routine code?

Any ideas as to why this runs in vb6 but not here?