macOS 11.0.1
Xcode version 12.2
Swift version 5.3.1

import UIKit

class ViewController: UIViewController,UICollectionViewDelegate,UICollectionViewDataSource{

    @IBOutlet weak var collectionView: UICollectionView!

    var array = ["あ","い","う","え","お"] //今回の配列の数は5個

    override func viewDidLoad() {
        super.viewDidLoad() 
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

         return array.count //cell数を配列の数に設定

    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for:indexPath)
        //タグ付けされたCell内のLabelにarrayのString値を入れる
        var arrayLabel = cell.contentView.viewWithTag(1) as! UILabel
        arrayLabel.text = array[indexPath.row] 

        return cell
    }
}

    //選択されたラベル値を受け取る
    var selectedArray:String?

    //didSelectItemAtでcellを選択した時の挙動を書く
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

        //選択したCell内のラベルがselectedArrayに代入される
        selectedArray = array[indexPath.row]
        //画面遷移
        performSegue(withIdentifier: "toNext", sender: nil)

    }

    //segueの準備
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        let nextVC = segue.destination as? NextViewController
        //遷移元のselectedArrayを遷移先のselectedLabelに渡す
        nextVC?.selectedLabel = selectedArray

    }

import UIKit


class NextViewController: UIViewController {

    @IBOutlet weak var textFiled: UITextField! 
    //遷移元で選択された値が入ってくる 
    var selectedLabel:String?

    override func viewDidLoad() {
        super.viewDidLoad()
        //渡ってきた値をTextFiledに渡す
        textFiled.text = selectedLabel

    }