Korean numbers can seem very difficult at first, but once you get the basics of how they work, it’s pretty easy….although I still have trouble with the native Korean numbers. These are just the basics, but the Sino numbers do go past 1000 of course. Too many zeros to fit in the graphic though!
Also remember that romanization is only a tool. Try not to depend on it too much. Learning the Hangul alphabet is the key to success!