Tinkercad is a group of tools that you can use for free to do 3D Modeling, construct circuits including Arduinos.
For 3D modeling it does not have as many tools as Blender or Fusion 360 however can be much faster to make prototypes.
The circuits allow you to quickly test your products without having to work with any of the physical electronics. It also allows you to prototype your code to ensure that it is working.
Using your school account
Try to make something
TinkerCAD
3D printed models will only come out in one colour but you can paint or apply stickers to recolour the finished product.
.stl is the Preferred filetype
The basic shapes will only let you design a limited range of objects. In the drop down menu you might want to look at the other options including Characters and Shape Generators
Use your school account