Travelling from Vancouver to Kathmandu

We are Canadian citizen flying from Vancouver to Kathmandu via Kunming and Nanjing. We are travelling to Kathmandu from Vancouver on February. The itinerary stated 1 layover, but technically it may be two - one in Kunming and other in Nanjing. We would fly from Vancouver to Nanjing (arriving at 14:45) and Kunming (arriving at 19:35) where we would have an overnight layover. Our flights to Kathmandu left the next day at 16:05. In total technically we will be nearly 26 hours in China (counting starts from Nanjing?). Do we need visa in advance or we can get on arrival? Where will we get our visa at Kunming or in Nanjing?