After the first evaporation, the water tank has 6000 liters - 2000 liters = <<6000-2000=4000>>4000 liters.
After the second extraction, the water tank has 4000 liters - 3500 liters= <<4000-3500=500>>500 liters
The tank is refilled with rain 30 minutes / 10 minutes = <<30/10=3>>3 times
The amount of water refilled with rain is 3 times * 350 liters per time = <<3*350=1050>>1050 liters.
With the additional rainwater, the water tank has 500 liters + 1050 liters = <<500+1050=1550>>1550 liters.
#### 1550