you can play with this for a start
(or post a short version of the json data as text)
JSONArray values;
void setup() {
values = loadJSONArray("new.json");
for (int i = 0; i < values.size(); i++) {
JSONObject animal = values.getJSONObject(i);
JSONArray values2 = animal.getJSONArray("bboxes");
JSONArray values3 = values2.getJSONArray(0);
float id = values3.getFloat(0);
println( id );
}
}