adding Adsense's In-Article Ads between images of blog post

My blog post contains only images like this

img class="aligncenter wp-image-567 size-full" src="..myimage_src_01.." alt="" width="960" height="960" /br/
img class="aligncenter wp-image-567 size-full" src="..myimage_src_02.." alt="" width="960" height="960" /br/
img class="aligncenter wp-image-567 size-full" src="..myimage_src_03.." alt="" width="960" height="960" /br/
img class="aligncenter wp-image-567 size-full" src="..myimage_src_04.." alt="" width="960" height="960" /br/

I've got script code form Google Adsense In-Article Ads

 script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"/script
ins .....xxx....data-ad-layout="in-article"/ins
script
     (adsbygoogle = window.adsbygoogle || []).push({});
/script

Let's say I've 9 images in my blog post , I want to show this In-Article Ads after each end of 3 images .
Like this ..

image
image
image
ads
image
image
image
ads
image
image
image
ads

I've tried Ad Inserter Plugin but it only have option for adding adsafter paragraph .
How can I format my post to enable like this ??