If you have a bunch of old +5v powerblocks with barrel connectors, then you may think they are worthless. Not so you can now get adapters to keep using the old powerblocks with your Raspberry Pi.
With the adapter, you can still use the power block as you always have and no soldering required.
You could also adapt an old computer power supply. Dangerous!! Wrongly set up it could KILL you Do not do this without expert help. Every power supply is different so you will have to tget the pinout for your power supply to be used. Do not do anything while the splly is plugged in on or off!!!! Suggestions: User your favorite search engine.