Then google it. There are hundreds, if not thousands of examples out there. If you find some, create your menu, and then STILL have trouble, THEN you can ask, when you've tried to fix it yourself, have some code to provide us with, and so forth and so on. We're not free coders - if you want someone to make your dropdown for you, hire someone.
Use this thread and posts for your reference, ask if you need something: https://forums.digitalpoint.com/thr...o-line-up-can-you-help.2767493/#post-19252667