Need help trying to make enemy detect player's projectiles

Fished out what bugs I could, I recommend you look into basic OOP, there are a lot of places where your trying to call a variable out of scope or are trying to create a variable without naming it. Note that in it's current state, the ship will only detect a bullet that existed before the ship did (as you are scanning for bullets in Awake()).

 using UnityEngine;
 using System.Collections;
  
 public class EnemyControllerBasic : MonoBehaviour {
      // The different IDS for the AI states
      enum AIMode { Normal, Ramming, SteerTowards, Avoid };
  
     private AIMode currentAIState = AiMode.Normal;
     private GameObject playerShip;
     private GameObject bullet;
     private PlayerShipCtrl playerController;
     
  
  void Start () {
     // find the player ship game object by name
     playerShip = GameObject.Find("PlayerShip");    
     bullet = GameObject.Find("PlayerProjectile");
     // Acess the player ship's script component by type
     playerController = playerShip.GetComponent<ShipPlayerController>();
  
  }
  // Update is called once per frame
      void Update () {
          transform.position +=
                 transform.up * Time.deltaTime * MoveSpeed;
          
          // Decides which AI state should be currently active
          DetermineAIState();
          EnemyPickup();
  
          // Depending on the current Ai mode
          switch (currentAIState)
          { 
              // Normal STATE
              case AIMode.Normal:
                  UpdateNormal();
                  break;
              // Rammin State
              case AIMode.Ramming:
                  UpdateRamming();
                  break;
              // STeer towards the player
              case AIMode.SteerTowards:
                  UpdateSteerTowards();
                  break;
  
          }
          
       
      }
  
  void UpdateNormal() { 
          // Move the object in the direction is facing
          transform.position +=
              transform.up * Time.deltaTime * MoveSpeed;
      
      }
      void UpdateRamming() { 
          // move the object in the direction it's facing
          transform.position +=
                  transform.up * Time.deltaTime * MoveSpeed;
      
      }
      void DetermineAIState() {
          bool canSee = CanSeeTarget("PlayerShip");
  
          // Subtract the enemy current position from the player
              Vector3 directionToPlayer =
                  playerShip.transform.position - transform.position;
  
  
              // Dot product of two vectors represent a cosine angle between them
              float product = Vector3.Dot(transform.up, directionToPlayer);
  
              // Convert the cosine value to a radian angle
              float angle = Mathf.Acos(product);
  
              // Convert the radian angle into a degree angle
              angle = angle * Mathf.Rad2Deg;
          if (canSee)
          {
              // If so, change to ramming mode
              currentAIState = AIMode.Ramming;
              
          }
          else if (product > 0 && angle < 90)
          { 
              // Change the state to steertoward
              currentAIState = AIMode.SteerTowards;
              // Change its color to green to enote
              renderer.material.color = Color.green;
          
          }
          else
          {
              // If not, return to normal state
              currentAIState = AIMode.Normal;
              renderer.material.color = Color.white;
              
          }
          
      }
  
      // Determines if the this AI can "See" the player
      bool CanSeeTarget(string _targetTag)
      {
          // Contains data about collision
          RaycastHit hitInfo;
  
          // Performs a ray cast
          bool hitAny = Physics.Raycast(transform.position, transform.up, out hitInfo);
  
          if (hitAny)
          {
              if (hitInfo.collider.gameObject.tag == _targetTag)
              {
                  return true;
              }
  
          }
  
          return false;
      }
  
  void UpdateSteerTowards() { 
       // Subtact the enemies current position from the player
          Vector3 directionToPlayer =
              playerController.transform.position - transform.position;
      // rotate the enemy's movement direction 
          transform.up = Vector3.RotateTowards(transform.up,
                                              directionToPlayer,
                                              Time.deltaTime * MoveSpeed,
                                              0.0f);
          UpdateNormal();
      }
  
  void UpdateAvoid() {
          Vector3 directionToProjectile =
              bullet.transform.position + transform.position;
          transform.up = Vector3.RotateTowards(transform.up,
                                                  directionToProjectile,
                                                  Time.deltaTime * MoveSpeed,
                                                  0.0f);
      
      }
      
  }