6
Free 3d designing software
(beehaw.org)
Onshape has a free hobby license. It's pretty easy to use and has lots of tutorials. You can draw a shape that you want and then extrude it into 3 dimensions.
Tinkercad
But you should tell us what it is that you want to make
FreeCAD for GUI, OpenSCAD for programatic.
For everyhting 3D printing related.
Please be excellent to each other :)
Icon by Freepik, Banner photo by Thiago Medeiros Araujo