How to install AWS rack

This command no longer work with convox 3:

convox rack install aws --name production4 VPCCIDR=4.0.0.0/16 Private=Yes Subnet0CIDR=4.0.1.0/24 Subnet1CIDR=4.0.2.0/24 Subnet2CIDR=4.0.3.0/24 SubnetPrivate0CIDR=4.0.4.0/24 SubnetPrivate1CIDR=4.0.5.0/24 SubnetPrivate2CIDR=4.0.6.0/24

Showing something like this:

Error: Unsupported argument

  on main.tf line 13, in module "system":
  13: 			VPCCIDR = "4.0.0.0/16"

An argument named "VPCCIDR" is not expected here.

ERROR: exit status 1

Wonder where to find documents regarding new working syntax of convox? Feeling like getting lost everytime I try doing something with convox one in a while.