Hey @joaoperfeito 

I am not sure if I understand your question correctly,

A person will only receive emails from the flow, if they left a product behind during the checkout process. The flow is triggered only when they “start checkout” and didn’t place an order yet.

So you would essentially have a flow filter, that says “placed order zero times since starting this flow” and so only the profiles who left behind a product during the checkout process will receive emails from this flow and the image will show of the product they left behind.

If you are asking how to create that dynamic block that shows the image, you can read more about it here 

Does this help you answer your question? 
Let me know if you have further questions. thank you for sharing your question here in the community

Cheers,