To form a number between 20 and 100, we use the same principle: Base number + digit.
23 = twenty-three, 33 = thirty-three, 43 = forty-three, etc.
To form a number with 100, we say “One hundred + and + base number + digit
123 = One hundred and twenty-three.
234 = Two hundred and thirty-four
345 = Three hundred and forty-five
To form a number in with thousand, we say “one thousand + one hundred + and + digit”
1234 = One thousand one hundred and thirty-four.
2345 = Two thousand three hundred and forty-five.