What can I do to treat 3 possible torn tendons (achilles, peroneal, and posterior tibial tendons)?

Rest. It is important to determine if the tendons are, in fact, torn. You may need to have an MRI to do this. If they are torn, they may need to be repaired surgically. Otherwise, depending on the severity of the strain or partial tear, rest and anti-inflammatory medications with off loading would be indicated.