I am a bit confused using datasource. I am new comer for TF, it is tall task for me

Terraform
1

We have naming standard for creating Resource Group and it is created by different via ticketing system. For that we if I request a resource group for dns. The system will create rg-dns-region for all the regions.
I want use the region created above using data source.

data "azurerm_resource_group" "rg" {
  for_each = toset(["eastus", "westus", "westus2", "westus3", "southcentralus", "westcentralus", "northcentralus"])
  name     = "${"rg-dns"}-${each.value}"
}
output "rg_name" {
  value = [for g in data.azurerm_resource_group.rg : g.name]
}

The above command yield the following output.
Outputs:

rg_name = [
  "rg-dns-eastus",
  "rg-dns-northcentralus",
  "rg-dns-southcentralus",
  "rg-dns-westcentralus",
  "rg-dns-westus",
  "rg-dns-westus2",
  "rg-dns-westus3",
]

The above script works for the output but not able to tie the storage account creation.

#Storage Block
resource "azurerm_storage_account" "storage" {
  for_each = toset(["eastus", "westus", "westus2", "westus3", "southcentralus", "westcentralus", "northcentralus"])
  name = lower("sadns00${each.value}")
  resource_group_name       = [for g in data.azurerm_resource_group.rg : g.name]
  location                  = each.key
  tags                      = var.resource_tags
  account_kind              = "StorageV2"
  account_tier              = "Standard"
  account_replication_type  = var.replicationType
  enable_https_traffic_only = true
  min_tls_version           = "TLS1_2"
}

│ Error: Incorrect attribute value type
│
│ on storage.tf line 19, in resource “azurerm_storage_account” “storage”:
│ 19: resource_group_name = [for g in data.azurerm_resource_group.rg : g.name]
│ ├────────────────
│ │ data.azurerm_resource_group.rg is object with 7 attributes
│
│ Inappropriate value for attribute “resource_group_name”: string required.

Can someone please assist me what I am missing. I feel like I am close but I could not figure out how to create storage account using for loops.