I assume that you already know that Korean sentences have different word orders. "~게끔" means "a purpose" of the latter part of the sentence, usually. "끔" is just for emphasis here. In most cases, you can instead say "~게". "~게끔" can be translated into English in several ways, because in English, there are many similar expressions to say a purpose like "for ... ", "to ..", "in order to..", ".. so that ...", etc. For example, 책꽂이의 저 책을 꺼낼 수 있게끔(or 있게, 있도록), 사다리를 빌려주세요. Please let me borrow your ladder so that I can reach the books on the book shelf and pull them out. 늦지 않게끔, 서둘러라. = 늦지 않게, 서둘러라. = 늦지 않도록, 서둘러라. You'd better hurry up not to be late.