Till 2016, NATA was online so there were no question papers available. However last year also the authorities have not released the question papers. The syllabus can be checked here - https://engineering.careers360.com/articles/nata-syllabus. What I suggest is that there are many online sample papers available. You could use them to practice. Maths is pretty much the Class 12 level. General aptitude and drawing, you could check some of the online sites or some books available in the market.