Introducing 3 chinchillas

I have 3 female chinchillas who are not related. They have been living next to one another for almost a year. There has not been any fighting at all through the bars of the cages. Could all 3 live togeather in the biggest cage, which is 4 feet tall, 3 feet wide and 2 feet deep? If so, how would I go about introducing them? Should I do it 1 at a time or all at once?

Thank you for any help:)