https://duet3d.dozuki.com/Wiki/Choosing_the_power_supply

https://duet3d.dozuki.com/Wiki/Choosing_a_bed_heater

And if you want to see what a conversion to Duet looks like in broad strokes take a look at this guide series.
https://duet3d.dozuki.com/Guide/Ender+3+Pro+and+Duet+Maestro+Guide+Part+1:+Wiring/37