Find a lot of research
Six pages is approximately 1500-1800 words. Pick a bigger topic. Find a lot of research. Do write in a succinct manner, but fill up the pages with details, justification, and analysis. Don't think of it as a more paper, however as a deeper paper, with a wider base of understanding to be shown to your teacher.
Aside from this, a 6 page paper is written exactly the exact same way as a 2 page paper. The difference is that rather than developing a stage in 1 paragraph, you might have to explain the finer details in greater detail, using several paragraphs. Where you would use a couple of sentences in a brief essay, you may develop those sentences to a paragraph using more description, exemplification, causal analysis, classification, definition or procedure.
I suggest making a summary or a brain map so you are able to capture and organize your thoughts on your native language before you start writing. Then you can concentrate on getting the info in good order before you begin massaging it into English.
Don't write long, fuzzy sentences, as that won't improve your quality. Don't be repetitive. A long essay needs more stuff, so do more research and do more thinking about the context and the significance of the topic.