how to make a high voltage dc transformer?

To create a high voltage DC transformer, you actually need a high voltage DC converter rather than a traditional transformer, as transformers only work with AC. You can use a DC-DC converter, such as a boost converter, which steps up the voltage. This involves using an inductor, a switch (like a transistor), a diode, and a capacitor. The switch periodically opens and closes, storing energy in the inductor and releasing it to produce a higher voltage output.