Hi@akhtar,
You can provide the value of each module variable when calling the module itself in Terraform.
module "folder" {
    source = "../<path>/"
    folder_name = "xyz"  # add this line to define the folder_name variable
}
If you'd like to specify folder_name on the command line instead, you can create a variable in your main.tf file and provide that via the command line instead.
variable "module_folder_name" {
  default = "xyz"
}
module "folder" {
   source = "../<path>/"
   folder_name = "${var.module_folder_name}"
}
And, then provide this variable's value via the command line.
$ terraform apply -var="module_folder_name=abc"