Question: My first year undergraduate teammate has submitted our project work to multiple conferences. I want him to pull back the submission before reviewers take action against us. But he wants proof that conferences actually care about it and can detect self plagiarism and double submission.

This is in electronics, where conference proceedings count as publications.

Answer: 
"Actually care about it": Read the conference's rules.

"Can detect": Irrelevant. Like many things in academic research, this is primarily honor system. If your teammate thinks that whether something is acceptable is determined by whether you can get away with it, they need a serious attitude adjustment.

By the way: do you have a faculty advisor on this project? They need to know about this. They would also be the best one to give you advice on the specific norms of conferences and publishing in your fields.
As a reviewer I routinely search for the paper title, basic paper keywords, and/or the particular combination of authors' names in an academic search engine. This typically shows the close environment of peers, a sub-sub-area, so to say.

But not once or twice this has resulted in rather unexpected results, such as a very similar titled paper with paragraph-wise text overlap and an author subset/superset.

This greatly saves my work time, because in the above case I can immediately flag it as plagiarism, send my review with snarky remarks to the editor, and go back to whatever I did before reviewing. I have yet to encounter a *true* double submission, but my actions would bear a strong degree of similarity.

*(You notice by now some degree of irony here, but I really have seen such plagiarism cases as a reviewer.)*