Exercise that builds muscle, aerobic exercise that increases lung capacity, these are going to be helpful to your lungs. The muscles that help the lungs include the diaphragm. When you breathe in, your diaphragm contracts and moves downward thus increasing the space in your chest cavity. This is the space into which your lungs expand. Yoga breathing is beneficial. Other muscles that help the lungs are the intercostal muscles.
These lie between your ribs so also help to enlarge the chest cavity. When you breathe in, they contract, pulling your rib cage upwards and outwards. It's a good idea to seek the exact exercises, such as yoga breathing, you need for helping the lungs from a fitness instructor or a physiotherapist. For a good outcome, you must exercise regularly and often.