Check out example codes for "change textmesh pro text". It will help you in understanding the concepts better.

Code Example 1

using UnityEngine;
using System.Collections;
using TMPro;

public class ExampleClass : MonoBehaviour
    void Example()
        TextMeshPro textmeshPro = GetComponent<TextMeshPro>();
        textmeshPro.SetText("The first number is {0} and the 2nd is {1:2} and the 3rd is {3:0}.", 4, 6.345f, 3.5f);
        // The text displayed will be:
        // The first number is 4 and the 2nd is 6.35 and the 3rd is 4.

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