how to validate mobile number in html form

<div>
  <label for="phone">Enter your phone number:</label>
<input type="tel" id="phone" name="phone"  pattern="+94[7-9]{2}-[0-9]{3}-[0-9]{4}" value="+94">
 </div>

  <div class="input1">
      <input type="tel" placeholder="telephone">
      <p class="info">Telephone must be a valid US number (11 digits)</p>
    </div>