This has to be done in Defense mode. First survive until night 9. E.g. get a chainsaw in wave 2 and save up. Then buy all the discounted mines you can until night 9. You should easily get something like 200 mines. Then plant them literally everywhere you can (there's a roughly circle-shaped area around the light pole that you can plant structures). Then stand in the middle of the level by the light pole and do nothing (you may walk if necessary).