How do I make my joint slerp from 1 rotation to another?

I am stuck trying to get my axis to rotate to a certain point but I am stuck because Transform doesn’t contain the definition for slerp and I can’t change my transform to quaternion because quaternion doesn’t contain the definition for rotate ;-;

using UnityEngine;
using System.Collections;

public class physics : MonoBehaviour {

    public Transform StartingPosition;
    public Transform Target;
    void Start()
        transform.rotation = Quaternion.AngleAxis(90, Vector3.down);
        Target.rotation = transform.rotation;
        Target.rotation = Quaternion.AngleAxis(180, Vector3.up);
	// Update is called once per frame
	void Update ()
        transform.rotation = Quaternion.Slerp(StartingPosition, Target, Time.deltaTime);

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