The gestation period for livebearers is around 4 weeks. And your fish looks pretty close to dropping them, probably in the next few days. Have lots of plants in the tank and don't move her. If there are males in the tank, move them out and leave the female with lots of plants. Keep males and females separate for at least 1 week after she gives birth. Don't move the female for at least 1 week after she has given birth.