if your assignment is to create a 3D model without using any 3D modeling tools, then that is … odd. three.js is not a 3D modeling tool. You could use the three.js editor and add boxes and cylinders to create a shelf, I suppose. It will look quite basic but will work.
Beyond that, you are going to have to make a real attempt, and then ask for help if you get stuck — we are not going write a bookshelf-making tutorial just for you. Please show that you are trying to solve the problem yourself before asking others to solve it for you.