beginner in paraview (problem with variable)

Hello !
I’m a beginner in paraview and I have a problem. I created a .stl file on the website tinkercad. I wanted to use paraview to visualize stream flows but when I open my file I don’t have any variable, I only have “the object”. How can I add variables to my file (3 are required to use the stream tracer) ?

STL file cannot store simulation data, it only stores a triangle mesh surface. At first, you need to convert your geometry and simulation data to another format available in ParaView such as *.vtu, etc.