What are the correct Shopify variables for the Meta pixel code?

I have a problem regarding the Shopify variables for the Meta pixel code. In general I know what to do and the pixel is working on my website (iqhorse.de) but I cannot find the correct Shopify variables for the standard events...or am I missing something? I've read a few references but I'm not able to create the correct code. content_name; currency, and value is working fine regarding my code snippet below but what is the correct Shopify variable for content_ids?

for example this is what I put in my header:

fbq('track', 'ViewContent', {
    content_ids: '{{ }}',
    content_name: '{{ product.title }}',
    currency: '{{ shop.currency }}',
    value: '{{ product.price | money_with_currency }}',
  });

Where can I find the variables for lets say the "InitiateCheckout" event like name, last name, browser-id, facebook login id etc...because thats what the Meta Event Manager asks me to do;-) How can I separate the event-ids to avoid deduplication?

Thanks in advance for any hint!

Regards from Germany