Fire a FB Pixel if a specific product is purchased

[fenglim92]

Hi all, 

Appreciate if anyone could point me to the right direction. 

I want to offer a "FREE TRIAL" product on my store for 1st time user to purchase & try. Absolutely free.

I want to fire a FB pixel event, ie "LEAD" when a user make a purchase that contains this specific "FREE TRIAL" product, on the /thank_you page. 

Is this possible? How can I achieve it? 

Thank you.