PrintABlok:Electroblok

Electrobloks, the interlocking DIY electronics learning kit. PrintABlok:ElectroBlok add common hobby electronics components like Arduino, servos, buttons, LEDs, and others, for rapid electronics prototyping allowing you to make printablok creations that can play with you!

Electrobloks require electronics components that are then modified and inserted into the bloks. If you do not have these common components, the list below will give you suggested sources for them. But a simple starter kit like the Elegoo Uno Basic Starter Kit (Affiliate link in the PDF) will usually get you started (and there are pre-plated STLs specific to the Elegoo Uno Basic Starter Kit that you can use to get started easier)
There's also pre-plated STLS for the Sparkfun's Inventor Kit (Affiliate link also in PDF) if that's more your style.
https://www.sparkfun.com/products/15631

Or you can just search the parts.zip for the specific components you may have laying around. If there's a component you want to p