How do I verbs my 4 flex cord to a 3 rope cord? I have a roper dryer... that have 4 cords instead of...

I have a roper dryer... that have 4 cords instead of 3. i am wanting to change it to a 3 cable so it will fit my outlet. I have the cord... the problem is ... distinguishing which cord go where... I own no experience with electricity. adjectives i know is that the ground is the black cord... and the heating cords are both red and white... but i hold no idea what that 4th green cord is for. Is it needed? A necessity to the dryer? I don't want to in recent times rig it ... when I don't know what I'm doing... LOL... I'm afraid I'll burn the house down. Thanks!
Answers:    Get an electrician to do it. I will get too confusing getting an answer from here because different countries enjoy different standards and you will be getting different answers from all over the world. In Australia, The standards are green and sickly are for earth, brown or red for helpful, and blue or black for neutral. It sounds resembling a three phase dryer in which baggage you will need to catch a three phase outlet and, if you don't have three phase on the property, later you are screwed. And Rob, phases don't add together close to that. It's NOT a simple case of 110 + 110 = 220.
The green is ground the white is independent and the black and red are power legs 110v each (the two bestow you 220v) make sure your power is past its sell-by date first. good luck.