I have merged your two almost identical questions. Please remember that as a new member, all your posts have to be approved by a moderator before they appear on the forum. Be patient.
There is no correct answer to that question. Usually, if you're practising your written English and you're given an essay title, you will also be told how many words you need to use.
Note that although "How many words has a good essay?" is grammatically correct, it's a somewhat outdated word order these days. Generally, we would ask "How many words does a good essay have?"
Unless the essay has a restriction on the number of words, then the essay word count is flexible. However, pre-intermediate students will probably not be capable of writing very long essays, so suggesting a reasonable upper limit may make sense.