You should check out habitat for humanity stores for rull appliances, generally anything above a microwave isnt likely to be found at Goodwill. I recommend Craigslist for sale of an appliance.
They take small kitchen appliances. If the microwave oven is in good working condition, they will likely accept it. If it is an independent electric range (not part of a whole oven assembly) then they may tale that, but will not accept an entire oven/range combo.
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