How to Remove the form value After Submit in React from below code?

So, In order to remove the reset the form you should use the controlled forms. By controlled forms i mean using the states to change form inputs. And that's the recommended way and best practice.

so if you'll have to re-write your your code it'll look something like this.

    import React ,{useState} from 'react';  // import useState hook
    import { Form } from 'react-bootstrap';
    
    const AddItem = () => {
    // Initialise  Values with empty string or null;
    const [inputeVal, setInputVal] = useState({
       carName:"",
       companyName:"",
    });
    
   const handleChange = (event)=>{
   const {name, value} = event.target;
   setInputVal({...inputVal, [name]:value}) // will set the values from input field to relevant state

   }
    
   const handleItemSubmit = () => {
      // your handle submit logic goes here 

     // after submit you can reset the form by resetting the states

     setInputVal({
        carName:"",
        companyName:"",
     })
    
        }
        return (
            <div className='w-50 mx-auto mt-5 py-5 d-block'>
                <Form onSubmit={handleItemSubmit}>
                    <Form.Group className="mb-3" controlId="formBasicCarName">
                        <Form.Control onChange={handleChange} value={inputVal?.carName} name="carName" type="text" placeholder="Enter Car Model Name" />
                    </Form.Group>
    
                    <Form.Group className="mb-3" controlId="formBasicCompany">
                        <Form.Control onChange={handleChange} value={inputVal?.companyName} name="companyName" type="text" placeholder="Enter Company Name" />
                    </Form.Group>
                    <button className='btn btn-primary' variant="primary" type="submit">
                        Submit
                    </button>
                </Form>
            </div>
        );
    };
    
    export default AddItem;

Just add at the end of function

event.target.reset();

Easy fix is to reset the form like this.

  const handleItemSubmit = (event) => {
    event.preventDefault();
    const carName = event.target.carName.value;
    const companyName = event.target.companyName.value;
    console.log(carName, companyName);
    event.target.carName = "";
    const inputField = document.getElementById("form");
    inputField.reset();
  };

And don't forget to Provide the id to your form

<Form onSubmit={handleItemSubmit} id="form">

However, i will highly suggest you to look into callmeizaz answer above about the useState. Thats the proper way to handle form