I need help calling an array to display the days corresponding to the months selected from a drop down list. I have tried every possible tutorials and forums and I can not find any that help me compr

I need help  calling an array to display the days corresponding to the months selected from a drop down list. I have tried every possible tutorials and forums and I can not find any that help me comprehend how to do this.

I just need help with the javascript code no other coding in html or css necessary I have already done that and this is my test files so that I do not mess with my original files.