<input type="text" name="Phone Number" pattern="[7-9]{1}[0-9]{9}"
title="Phone number with 7-9 and remaing 9 digit with 0-9">
<form action="/action_page.php" enctype="multipart/form-data" >
<label>Name</label>
<input type="text" name="name" pattern="[A-Za-z0-9]{3}" ><br><br>
<input type="submit">
</form>