Where to find Checkout Page and Add to Cart CSS Selectors?

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Hi all, 

I am trying locate the Checkout Page CSS Selector and Add to cart CSS Selector on my Shopify site. I am using the Showcase them and the support didn't help me with this. Wondering if anyone can point me how to find this. I am not trying to make changes, I simply need to know what are those selectors for my theme on my site. 

This is my site https://jgcontemporary.art. 

Much appreciated in advance.