今天收到移民局的来信，老公2007年7月以绿卡持有人配偶的名义提出的申请得到批准，信上的内容如下：
The above petition has been approved. We have sent the original visa petition to the Department of State National Visa Center. NVC processes all approved immigrant visa petition that need consular action. It also determines which consular post is the appropriate consulate to complete visa precessing. NVC will then forward the approved petition to that consulate.
我有点不太明白之后的程序到底是什么，我是否需要离境等待？还有大致还有多长时间我可以转换身份？请各位大侠帮帮忙，万分感谢！