I have a large HTML Form and it has multiple fields in multiple components.

All these components are in a Parent Component.

How Can I submit a form and getting values from all child components?

```
<form>
  <Col md={6} className="mb-3">
     <SameDay />
  </Col>
  <Col md={6} className="mb-3">
     <International />
  </Col>
  <Col md={6} className="mb-3">
     <OutBondTracking/>
  </Col>
  <Col md={6} className="mb-3">
     <FulfilmentOptions />
  </Col>
  <button
    type="button"
    className="btn btn-primary mr-2"
    onClick={() => this.submitHandler()}
  >
    Submit
  </button>
</form>

```