How to create proxmox VM's with /64 or /56 subnet?

I searched online and only saw a few forum posts about it, but nothing was really helpful.

I do not want to use IPv4 anymore, because it is too expensive for my usecase, since i deploy a lot of ubuntu 24.04 server VM's.

I have used Proxmox for a few months now and i finally start to slowly understand everything, but i need help with this. I also asked AI, but it wasn't really helpful.

If there is a guide to do it then please send me the link.