Get private IPs from ENIs of NLB

Terraform Providers AWS
1

how to Get private IPs from ENIs which got created for RDS instance and attach to NLB . it tried below it dint work

data "aws_network_interfaces" "get-eni" {
  filter {
    name   = "subnet-id"
    values = [aws_subnet.customer_subnet_1.id, aws_subnet.customer_subnet_2.id]
  }

  filter {
    name   = "description"
    values = ["RDSNetworkInterface"]
  }
}

resource "aws_lb_target_group_attachment" "tga-pac" {
  target_group_arn = aws_lb_target_group.tg-pac.arn
  port             = 5432
  target_id        = formatlist("%s/32", [for eni in data.aws_network_interface.get-eni : eni.private_ip])  
  depends_on       = [aws_db_instance.pac_postgres]

Error: Reference to undeclared resource

  on nlb.tf line 48, in resource "aws_lb_target_group_attachment" "tga-pac":
  48:   target_id        = [data.aws_network_interface.get-eni.private_ip]

A data resource "aws_network_interface" "get-eni" has not been declared in the
root module.