Hi@akhtar,
You can use aws_volume_attachment resource to attach an ebs volume. I have attached one example below for your reference.
variable "device_name" {default=["/dev/sdd"]}
variable "ec2_ebs_volume_count" {default=1}
resource "aws_ebs_volume" "ebs_volume" {
  availability_zone = aws_instance.myin2.availability_zone
  size = 2
  tags = {
    Name = "myebs1"
  }
}
resource "aws_volume_attachment" "ebs_att" {
  device_name = "/dev/sdd"
  volume_id = aws_ebs_volume.ebs_volume.id
  instance_id = aws_instance.myin2.id
  force_detach = true
} 
Hope this will help.