Build a function for 3D model

I need a function (in every language you can) that takes in input a STEP o STL file and 3 sizes (x,y,z), adds to the 3D model (loaded from the STEP/STL file) elementary volumes (cylinders and rectangular boxes) in order to create a bigger box with sizes x,y,z.
It returns in output added volumes (type, sizes and location). Write 'mela' in your message to verify you have read.

Write the programming language you will use.