For those of us outside the US and used to other units, a cord [1] is of course 128 cubic feet or roughly 3.62 cubic meters. The wood is supposed to be well stacked (aligned, parallel, touching and compact) and if so, one cord is a pile measuring e.g. 4x8x4 feet. Wow, three cord is "a lot", in other words.
Cords of wood are usually around 18 million BTU of potential energy, which is 5000+ kWh. Wood stove efficiencies are all over the place, but modern ones are in the 70% range.
[1]: https://en.wikipedia.org/wiki/Cord_(unit)