3D models of electronic components

some manufacturers provide models in several formats, including step
your design tool may have a variety of components with models already
your design tool may have various models already defined for the ICs you list
your design tool may have a 3D model (& footprint) generator built in

Try https://www.3dcontentcentral.com/ I used to get many from there.

I found the step files at the websites of Analog Devices and Texas Instruments. These step files contains 3D models of the components.

For most designs, just use the basic feature for extruding small devices such as resistors and caps. In fact for most designs to do an interference fit the basic extruded shape of the component volume will do. Using pretty models is only of benefit when you want pretty pictures of a PCB or you are doing silly tight designs (such as having a sintered heat spreader between boards in a sealed case, not fun to design), the extra geometry etc. add size to the text file etc.
I tend to avoid realistic models as said for small components, for a lot of basic stuff, realistic connectors will do.
Beware some of the component step files are done with surfaces, avoid these, they can cause issues later.
I had to draw my own models in the past as non were available in the early 2000's, we had to use IDF into a 3D package, then export the step file.