How to auto-populate data to textbox from DB

Question

I created a program and one of its function is when you select an item from the dropdownlist, the data from database will automatically populate to the textbox. I have 16 texboxes and problem was, when I click the a selection, only 1 data from the DB will populate to the 16 textboxes. To help me explain clearly, please see the attached picture of my codes and DB. By the way, I am only a novice in programming. Thanks you in advance.