NATIVE KOREAN NUMBERS

1 → 하나   2 → 둘   3 → 셋   4 → 넷   5 → 다섯   6 → 여섯   7 → 일곱   8  → 여덟   9 → 아홉

They're used to count hours, animals, sheets, cups, people, bottles, books, clothes, pencils, and things in general. 

10 → 열   20 → 스물   30 → 서른   40 → 마흔   50 → 쉰   60 → 예순   70 → 일흔   80 → 여든   90 → 아흔

Native Korean numbers have specific words for 20, 30, 40, etc, so to make all the numbers until 99 you'll just put the unit you need after 스물, 서른, 마흔, etc.

Eg: 13 → 열셋   45 → 마흔다섯   57 → 쉰일곱   82 → 여든둘

REMEMBER THAT the minimum existing Native Korean number is 1 and the maximum is 99, so if you need a higher one, you'll need to use the Syno-Korean numbers.