First say the first ten numbers, with music.
One, Two, Buckle my shoe
Three, Four, J't'dore
Five, Six, Pick up sticks
Seven, Eight, Lay them straight
Nine, Ten, Tell me when
Then just count from one to ten without the music.
Count past ten adding new numers slowly.
After fourteen pick up the pace until twenty is reached.
You should be able to advance quickly from twenty to thirty.