Load block as default for new post

I’ve found instructions how to add a Block Template but you need to know the path to the block — for example, a core Gutenberg image block is specified as:

‘core/image’

Can somebody please tell me how to find out what that path is for non-core blocks, e.g. the Atomic Blocks?

BTW, the (otherwise very clear) instructions/code I’m following is:
https://wp.zacgordon.com/2018/01/05/how-to-add-block-templates-to-your-wordpress-theme-or-plugin/

(All I want to do is load the AB Container Block for all new posts, and am spinning my wheels here – trawled for half an hour through endless pages of codex and online guides… I’m guessing it’s maybe so obvious, nobody puts it in the instructions!)

Thank you!