If you already have an old power adapter you can cut off the molex connector and use one of these. This is what I did.

https://www.amazon.com/Chanzon-Female-Connector-Security-Adapter/dp/B079RCNNCK/ref=mp_s_a_1_11?dchild=1&keywords=barrel+plug+to+screw+terminal&qid=1593091285&sr=8-11

Edit: you may be able to find a single piece or a male/female pair for less. I just used the 10 piece as an example.