There are a few ways too tell what sex your budgie is. One way is to grab your bird and hold it upside down and like it or not feel it's private parts I'm preety sure if there are two little balls close to each other it is a boy and two little balls far apart a girl correct me if I'm wrong
Two wait a few months and the cere will turn a colour if green or blue a boy if brown a girl
Hope this helped if wrong then reply and tell me
Bye