Getting error while deploying aws ec2 module

Terraform
#1

Hi Team , i was practicing aws ec2 instance creation using aws ec2 module and i want to deploy 2 ec2 instances for 2 subnet ids. But i am unable to do that , Can you please help me ?

Here is the aws ec2 module tf file that i am using

# private ec2 instance host 
module "private_instance" {
  depends_on = [module.vpc]
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = "4.3.0"
  count = length(var.instance_count)
  tags = {
    "Name" = var.instance_count[count.index]
  }
  ami                         = data.aws_ami.amzlinux2.id
  instance_type               = var.instance_type
  subnet_id = (var.vpc_private_subnets [count.index])
  user_data = file("${path.module}/app1-user-data.sh")
  vpc_security_group_ids      = [module.private-security-group.security_group_id]
  key_name = var.instance_keypair
}

And also i am creating vpc and my private subnets using vpc module

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "3.19.0"
  #version = "~> 2.78"

  # VPC Basic Details
  name            = "${local.name}-${var.vpc_name}"
  cidr            = var.vpc_cidr_block
  azs             = var.vpc_availability_zones
  public_subnets  = var.vpc_public_subnets
  private_subnets = var.vpc_private_subnets
  # NAT Gateways - Outbound Communication
  enable_nat_gateway = var.vpc_enable_nat_gateway
  single_nat_gateway = var.vpc_single_nat_gateway

  # VPC DNS Parameters
  enable_dns_hostnames = true
  enable_dns_support   = true


  tags     = local.common_tags
  vpc_tags = local.common_tags

  # Additional Tags to Subnets
  public_subnet_tags = {
    Type = "Public Subnets"
  }
  private_subnet_tags = {
    Type = "Private Subnets"
  }
  database_subnet_tags = {
    Type = "Private Database Subnets"
  }
}

And i am using 2 subnets for 2 ec2 instances meaning i want to create ec2 instance in each subnet

# VPC Variables
vpc_name                               = "myvpc"
vpc_cidr_block                         = "10.0.0.0/16"
vpc_availability_zones                 = ["us-west-2a", "us-west-2b"]
vpc_public_subnets                     = ["10.0.101.0/24", "10.0.102.0/24"]
vpc_private_subnets                    = ["10.0.1.0/24", "10.0.2.0/24"]
vpc_database_subnets                   = ["10.0.151.0/24", "10.0.152.0/24"]
vpc_create_database_subnet_group       = true
vpc_create_database_subnet_route_table = true
vpc_enable_nat_gateway                 = true
vpc_single_nat_gateway                 = true
#2

How can i use vpc_private_subnets variable (list of strings) in my ec2 tf file for subnet_id , Kindly help me

#3

To use the vpc_private_subnets variable (which is a list of strings) in your EC2 Terraform file for the subnet_id variable, you can use the count variable to iterate through the vpc_private_subnets list.

count = length(var.vpc_private_subnets)