I purchased a new window air conditioner and the voltage is 115 volts and 15 amps. My old window a/c required 230 volts 30 amps. How can I change or correct the voltage and amp for my socket. My current circuit breaker is 30 amps 2 pole.

Assuming 10-2 wire with ground.
Replace existing double breaker with 20 amp single breaker. Put black to breaker and white to neutral bar.
At outlet remove existing outlet, replace with 20 amp outlet matching A/C plug. White to silver screw, black to brass screw. You may have to add a pig tail of 12 gauge wire to existing 10 gauge wire to get wires under screws.