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So, if you look at the actual board of the trackball, you'll notice it's actually labeled as a USB connector -- [link] [link] -- so you can use something like -- CERRXIAN 1ft USB 2.0 to 5 Pins Screw Terminal Female Balum Charging and Data Transfer Converter Adapter Extension Cord (USB-A Male) [link] -- to connect to a computer.
My usual is just to chop a spare USB cable and solder it on. If you're not wanting to solder, you can try something like this -
The one that comes in kit #1 is Jameco part# 2227209 (you connect wires to it yourself from those included in the jumper wire pack)
The one Ben had in his video he made himself. If you want that you'd need to cut up your own USB cable and solder something to it to connect to the breadboard. I'd highly suggest only going that route if you have a bunch of unused USB cables laying around already, and a multimeter to verify the power/ground wires (the colors can lie)
Or you can get a similar USB-A to screw terminal adaptor such as this one.
Just don't plug it into a computer to get power. Use a phone charger or something that can provide 2 amps (A PC can only guarantee 0.5 amp, and will be a very expensive power supply to replace if you accidentally short circuit something)
Avoid future problems and get something like this instead