Good morning. Number lines for grades K-3 must be drawn as a graphic. You will find excellent guidance for the production of number lines in the lower grades in the new GUIDELINES AND STANDARDS FOR TACTILE GRAPHICS which you can view or download at this site:
By searching for the keywords "number line" you will be able to learn all about it. Unit 6 gives the details of any number line; 188.8.131.52 gives requirements for grades K-3. Unit 11 further discusses graphics for early grades. Blue underlined links take you to illustrative examples.
Let me know if you have further questions. Thanks for asking.