What power cord do I use for Mac Mini

as the others have said, it's an industrial std. ac cable then you should be able to find replacements for cheap in most supermarkets, av stores and electronic stores

The one that came with it.

All Mac mini’s from 2010 thru 2023 use the same stile of power cord.

https://www.google.com/search?

The connector at the Mini end is an IEC 60320 C7 coupler. The wire gauge is 18 AWG.

The other end is whatever your household or office receptacles require.