The Japanese number system is very unique. It is easy to learn and very straight forward, eventhough it can get lengthy and look overwhelming.

First we look at the easy part:
In English we have words like thirteen, eighteen, twenty, fifty, ninety.
The Japanese simply say ten three, ten eight, two tens, five tens, and nine tens respectively.
Japanese merely combine "how many" of "which position." 5 tens (50), 9 hundreds (900), or 2 thousands (2000).

To say fourteen it would be ten four (juu yon).

Twenty (20) in Japanese it would be two tens (niJuu).

Eighty-seven (87) in Japanese it would be eight tens seven (hachiJuu nana).

To say thirty-three thousand fourty-two (33,042) it would be three [ten thousands] four tens two (sanMan yonJuu ni).

Six hundred thousand (600,000) would be six [ten thousands] (rokuMan).

It gets really long with numbers like nineteen ninety-eight (1998) which would be one thousand nine hundreds nine tens eight (sen kyuuHyaku kyuuJuu hachi).
Or 99,887,766 which is kyuuSen kyuuHyaku hachiJuu hachiMan nanaSen nanaHyaku rokuJuu roku.

Don't let the length intimidate you, start with small numbers. Try doing very basic math with Japanese numbers until you are comfortable with the values that they represent. Most importantly Gambatte! (Hang in there!)