To find your collection handle go to the collection and then scroll to the bottom to the Search engine listing preview and click on "Edit website SEO", it'll show your url, title, and handle. Your handle is the last thing at the end of the url:
All handles are lowercase and spaces are separated by hyphens, special characters are not included. So whatever is there is exactly what you're going to need to copy and paste into the quotes of the unless statement.
Alright, I found the spot. You had to edit it in your product-card-grid.liquid and product-card-list.liquid snippets. I added the condition to both of them in the case you ever switch to a list in the settings. I am not really sure where you are editing that collection.liquid, as the one on your current store only has an include inside it for collection-template.
Anyway, take a look at the Ninthony Editing theme, just preview it. If it looks fine to you, you can publish it.