Just send an email to their public diplomacy service or press services if they have one, and ask them if it’s possible to get all three books delivered. They’ll be happy to know you’re interested.
Your embassy will be located in the capital of your country, you have to contact the Chinese embassy obviously, and they speak your local language.
Update: I just got my two copies, of volumes 2 and 3. For free. Volume 3 is only in Chinese and English for now though, if that’s important to you.
I’m gonna send them an email to thank them.