Hi Shivprasad
The Mendix API has some options
mx.ui.confirmation({
    content: "Do you really want to eat a burger?",
    proceed: "I really do",
    cancel: "I'll pass",
    handler: function() {
        console.log("eating burger");
    }
});
https://apidocs.rnd.mendix.com/9/client/mx.ui.html#.confirmation
For popup pages, use the nanoflow to show them
Cheers, Andries