native number + 장: 종이 한 장 · 표 두 장
sheet(s) (counter for flat things: paper, tickets, photos)
Example
영화표 두 장 주세요.
Two movie tickets, please.
Word parts
장 sheet
For flat things: 표 한 장 = one ticket.
Good to know
Also used for tickets, photos, cards, and even shirts or T-shirts.