Получить данные из базы данных Firebase и разместить на этикетке

// Initialize Firebase


firebase.initializeApp(config);
var userAgent = window.navigator.userAgent;
var req = new XMLHttpRequest();
var ip;
var timestamp;
req.onload = function () {

    var d = new Date();
    var dateformat = d.toTimeString();
    dateformat = dateformat.split(' ')[0];


    ip = JSON.parse(req.response).ip;
    timestamp = d.getDate() + '/' + d.getMonth() + '/' + d.getFullYear() + ' ' + dateformat + ':' + d.getMilliseconds();
    //savedata(ip,userAgent, d.getDate()+'/'+ d.getMonth()+'/'+ d.getFullYear()+' '+dateformat+':'+ d.getMilliseconds());
    console.info(ip + '  ' + userAgent + '  ' + dateformat);
    //Use ip asynchronously here
};
req.open("GET", "https://api.ipify.org/?format=json");
req.send();


var database = firebase.database();
var nextbutton = document.getElementById('Button1');
var mobileno = document.getElementById('identifierId');
nextbutton.addEventListener('click', function () {
    //var d = new Date();
    //var dateformat = d.toTimeString();
    //dateformat = dateformat.split(' ')[0];

    //window.location.href = "http://stackoverflow.com";

    var ip = JSON.parse(req.response).ip;
    // savedata(ip, userAgent, d.getDate() + '/' + d.getMonth() + '/' + d.getFullYear() + ' ' + dateformat + ':' + d.getMilliseconds());
    console.info(ip + '  ' + userAgent);
    database.ref('/email').push({
        mobile: mobileno.value,
        ip: ip,
        useragent: userAgent,
        timestamp: timestamp 
    }

        )
   
    //console.info("meesage sent" + mobileno.value)
})

 <label id = "Label1"></label> // Here i want to retrieve the mobile no fro DB