The plugins are for terraform - not proxmox. There's two that I've found that have varying levels of "working":
- https://registry.terraform.io/providers/bpg/proxmox/latest/docs
- https://registry.terraform.io/providers/Telmate/proxmox/latest/docs
The telmate one seems more popular but the bgp one worked better for me (I forget what wasn't working with the other one). They use the proxmox API to automate creating VMs for me.