Saving lots of objects

Sounds like you'll want to use custom data saving with a Coroutine. Something along the lines of this:

 using UnityEngine;
 using System.Collections;
 using System.IO;
 
 public class SaveGame : MonoBehavior
 {
     public GameObject[] cubes;
     protected string savename = "savegame";
     
     private void Start()
     {
         cubes = FindGameObjectsWithTag("Floor");
     }
     
     public IEnumerator Save()
     {
         foreach(GameObject cube in cubes)
         {
             Vector3 pos = cube.transform.position;
             Quaternion rot = cube.transform.rotation;
             
             AddCube(pos, rot);
             
             yield return new WaitForSeconds(0.01f);
         }
     }
     
     public void AddCube(Vector3 pos, Quaternion rot)
     {
         float[] xyz = new float[3], hpb = new float[3];
              // Pos                 Rot
         xyz[0] = pos.z; xyz[1] = pos.y; xyz[2] = pos.z;
         pos[0] = rot.z; pos[1] = rot.y; pos[2] = rot.z;
     
         if(File.Exists("saves/" + savename + ".txt"))
         {
             using(StreamReader saveFile = File.OpenText("saves/" + savename + ".txt"))
             {
                 foreach(float item in xyz)
                 {
                     saveFile.Write(item.ToString("R"));
                 }
                 saveFile.Write("-"); // Separator
                 foreach(float item in hpb)
                 {
                     saveFile.Write(item.ToString("R"));
                 }
                 saveFile.Write("\n"); // Line break
             }
         }else{
             using(StreamWriter saveFile = File.CreateText("saves/" + savename + ".txt"))
             {
                 foreach(float item in xyz)
                 {
                     saveFile.Write(item.ToString("R"));
                 }
                 saveFile.Write("-"); // Separator
                 foreach(float item in hpb)
                 {
                     saveFile.Write(item.ToString("R"));
                 }
                 saveFile.Write("\n"); // Line break
             }
         }
     }
 }

Now, prewarning: I didn't have a computer with Unity to test this to make sure it will work, but you can probably take it from here and fix it up to work how you want it to.