The below program will do the work
Imports System.Xml.Linq
Namespace MakeEnvVars
Class Program
Private Shared Sub Main(args As String())
Dim fileName As String = "D:\Web.config"
Dim doc As XDocument = XDocument.Load(fileName)
Dim message As String = String.Empty
Dim elements = doc.Descendants("appSettings").Descendants("add")
For Each element As XElement In elements
message = "SET {element.FirstAttribute.Value}=""{element.LastAttribute.Value}"""
Console.WriteLine(message)
Next
Console.ReadKey()
End Sub
End Class
End Namespace