What use to burn in power cords?

Thanks. But I'm not clear if I have to support the power cord so it doesn't touch the floor.

Shunyata suggest plugging into a fan for their "break in" adaptor

https://shunyata.com/products/accessories/burn-in-adapter/

What's wrong with just plugging the power cables in with a load (something turned on)?

If you have a high-resovling audio system (mid high-end) then raising the cables off the ground will make an audible difference.

If you are entry level high-end or lower you will likely not hear any difference from raising cables off the floor.