Call Interstitial Ads after 3 clicks

Hi, I am Manvir Singh and want to call Interstitial Ads after 3 clicks. Can any body make js code for me help me please…
Ad code:
var admobid = {};

// TODO: replace the following ad units with your own
if( /(android)/i.test(navigator.userAgent) ) {
admobid = { // for Android
banner: ‘ca-app-pub-xxx/zzz’,
interstitial: ‘ca-app-pub-xxx/kkk’,
rewardvideo: ‘’,
};
} else if(/(ipod|iphone|ipad)/i.test(navigator.userAgent)) {
admobid = { // for iOS
banner: ‘ca-app-pub-xxx/zzz’,
interstitial: ‘ca-app-pub-xxx/kkk’,
rewardvideo: ‘’,
};
} else {
admobid = { // for Windows Phone
banner: ‘ca-app-pub-xxx/zzz’,
interstitial: ‘ca-app-pub-xxx/kkk’,
rewardvideo: ‘’,
};
}

function initApp() {
if (! AdMob ) { alert( ‘admob plugin not ready’ ); return; }

// this will create a banner on startup
AdMob.createBanner( {
adId: admobid.banner,
position: AdMob.AD_POSITION.BOTTOM_CENTER,
isTesting: false, // TODO: remove this line when release
overlap: false,
offsetTopBar: false,
bgColor: ‘black’
} );

// this will load a full screen ad on startup
AdMob.prepareInterstitial({
adId: admobid.interstitial,
isTesting: false, // TODO: remove this line when release
autoShow: false
});
}

if(( /(ipad|iphone|ipod|android|windows phone)/i.test(navigator.userAgent) )) {
document.addEventListener(‘deviceready’, initApp, false);
} else {
initApp();
}

Js code:
function myAd() {
if(AdMob) AdMob.showInterstitial();
}