What was Sadako Sasaki's ambition for the future?
What did Sadako Sasaki want to be when she grew up?

After Sadako Sasaki died, her classmates started a campaign to build the Children's Peace Monument. They compiled memories of Sadako in a small book they called Kokeshi, which includes the following:

"When we all became sixth graders, including Sadako, a new teacher named Mr. Nomura came to teach our sixth grade class. Mr. Nomura really liked physical education, and we did some sort of PE every day. Sadako also loved PE. She was our best runner. She was also great at the vault. She would jump right over easily….For two semesters in a row Sadako was elected to the PE committee. She was also a very good student. She took good care of our class, even the boys."
From this we get an image of Sadako as a nice girl who was very good at sports.

Mr. Tsuyoshi Nomura, who is mentioned in that text, was in charge of Sadako's sixth grade class. According to the book Sadako, the Story of the Children's Peace Monument (Note), Sadako told Mr. Nomura that she wanted to be a junior high school PE teacher.

Note) Sadako, the Story of the Children's Peace Monument (in Japanese) was written by the NHK Hiroshima Nuclear/Peace Project and published by NHK Shuppan.