In English it is "two sheets of paper", not "two papers". Analogously, in Korean jang (장; 張) is used to count sheets or anything that is a paper-like material, for example:
버스
버스
beoseu
bus
표
票
pyo
ticket
열
열
yeol
ten
장
張
jang
'sheets'
버스 표 열 장
버스 票 열 張
beoseu pyo yeol jang
bus ticket ten 'sheets'
"ten bus tickets"
In fact, the meanings of counter words are frequently extended in metaphorical or other image-based ways. For instance, in addition to counting simply sheets of paper, jang in Korean can be used to refer to any number of thin, paper-like objects. Leaves (namunnip 나뭇잎) are counted using this count word. In this way, a particular count word may be used generally in a very open-ended manner and up to the construal or creativity of the speaker.
There are two systems of numerals in Korean: native Korean and Sino-Korean. Native Korean numerals are used with most counter words, and usually count the number of an object, while Sino-Korean numerals are generally used for indicating a specific object in series, such as a specific lesson in a book, as well as monetary units and scientific measurements. Sometimes both types of numerals may be used, usually native Korean numerals indicating a quantity and Sino-Korean numerals indicating an ordinal. For example:
열
열
yeol
과
課
gwa
열 과
열 課
yeol gwa
'ten lessons'
십
十
sip
과
課
gwa
십 과
十 課
sip gwa
'lesson ten'
There are exceptions, such as native Korean numbers being used with 시, meaning "hour of the day". Additionally some counters (mostly those associated with traditional units) modify the pronunciation and spelling of the numerals that precede it, most notably 6월 is 유월 and 10월 is 시월.
artworks, very small amounts, pieces of sliced or ripped-off flesh, drops of rain, stones in the game of Go on the board or captured from the opponent, or wisps of clouds or wind
^Typically, there are 20 cigarettes in a pack, and 10 packs in a bundle. 담배 스무 개비 = 담배 한 갑(匣), 담배 열 갑 = 담배 한 보루
References
^Martin, Samuel Elmo (2006). A reference grammar of Korean = Hanguo yu wen fa zong jian = Hanʼgugŏ munpŏp chʻongnam : a complete guide to the grammar and history of the Korean language. Clarendon, Vt.: Tuttle Publishing. ISBN0-8048-3771-6. OCLC496704267.