I suppose that I will need a step-down 220/110V transformer. I bought a 8000Wt one with 3 110V outlets. Does it mean that I have to connect 4 wires of an appliance to 1 positive, 1 positive, 1 neutral and 1 ground wire?
What color is neutral? Black?

Please restate your question, more clearly and more detail.

40 Amp appliances both dryer and dishwasher?

You bought one 8000 wt what?

A USA electric range would need 120/240.

Is the 8000 wt thing your 220 volt to 120/240 volt transformer?