Synchronize main loop (Spawner.cs) with subloop on Prefab

I'm working on Unity3d project where the floor has to unfold gradually. I created a script FloorModule.cs where using coroutine the floor tiles are laying out gradually. Each next module has to unfold right after previous is completed. There for I created Spawner.cs to loop a new FloorModule.cs right after previous one is completed.

I can't seem to get my head around how to use coroutine to synchronize the mainloop (Spawner.cs) with subloop on prefab (FloorModule.cs).

Here is the link to the example
https://1drv.ms/u/s!AkVZpIE6f1GV4M5Ju7G5zPOrQcCe8w?e=QrghRT

P.S.
In given example, as loop goes forward I'm using "Reference.cs" class to change some variable values .

FloorModule.cs

    public class FloorModule : MonoBehaviour
    {
        public float zSpacer = 0f;

        public int instPrefabCount;
        public Transform spawnPoint;
        public int lenght = 15;
        public int width = 5;

        public GameObject floorTiles;

        void Start()
        {
            spawnPoint = GetComponent<Transform>();

            StartCoroutine(FwFloorDelay(spawnPoint));
        }

        public IEnumerator FwFloorDelay(Transform origin)
        {
            for (int l = 0; l < lenght; l++)
            {
                float xAngle = 90;
                float yPos = 0;
                float zPos = 0 + l;

                for (int w = 0; w < width; w++)
                {
                    int xSelection = Random.Range(0, 6);
                    GameObject xFloor = Instantiate(floorTiles, origin);

                    TileStatusNames(xFloor, l, w);

                    // defining positiona and angles
                    float xPos = w + (zSpacer * w);
                    xFloor.transform.localEulerAngles = new Vector3(xAngle, 0, 0);
                    xFloor.transform.localPosition = new Vector3(xPos, yPos, zPos);

                    yield return new WaitForSeconds(.05f);

                }
            }

Spawner.cs

    public class Spawner : MonoBehaviour
    {
        public GameObject FloorModPrefab;
        public References[] referenceScript;

        void Start()
        {
            StartCoroutine(SpawnModules());
        }

        IEnumerator SpawnModules()
        {
            for (int i = 0; i < referenceScript.Length; i++)
            {
                referenceScript[i].instance =
                    Instantiate(FloorModPrefab, referenceScript[i].ref_spawnPoint.position, referenceScript[i].ref_spawnPoint.rotation);

                referenceScript[i].ref_instFloorModCount = i + 1;
                referenceScript[i].Setup();
                yield return new WaitForSeconds(5f);
            }
        }
    }

References.cs

    [Serializable]
    public class References
    {
        FloorModule prefabObjScript;
        public GameObject instance; 

        public int ref_instFloorModCount;
        public Transform ref_spawnPoint;
        public int ref_Width = 5;
        public int ref_Lenght = 15;

        public void Setup()
        {
            // Get references to the components.
            prefabObjScript = instance.GetComponent<FloorModule>();

            // Set the player numbers to be consistent across the scripts.
            prefabObjScript.instPrefabCount = ref_instFloorModCount;
            prefabObjScript.spawnPoint = ref_spawnPoint;
            prefabObjScript.width = ref_Width;
            prefabObjScript.lenght = ref_Lenght;
        }
    }

I tried to use coroutines unfortunately in given context I realize it's impossible for me to resolve this task.

You can yield a coroutine from within another coroutine.

Changes to your Code

In References change public GameObject instance; to public FloorModule instance;
In Spawner change public GameObject FloorModPrefab; to public FloorModule FloorModPrefab;
Remove the code from Start of FloorModule.

Modify FwFloorDelay to

public IEnumerator FwFloorDelay(Transform origin = null)
{
    if (origin == null)
    {
        origin = transform;
    }
    ...
}

In SpawnModules, chain the floor delay coroutine

IEnumerator SpawnModules()
{
	for (int i = 0; i < referenceScript.Length; i++)
	{
        ...
		yield return referenceScript[i].instance.FwFloorDelay();
	}
}

Your goal should not be to synchronize separate coroutines, but rather to get the code running sequentially in one coroutine.

For example, you could make References.Setup() asynchronous, and then have it invoke FloorModel.FwFloorDelay directly instead of the FloorModel starting its own separate coroutine.