Create a script (replacing the variables as necessary) and run it to replace ALL instances of (in this case) “star.jpg” to “star.png”

<?php

// CHANGE THESE VARIABLES TO MATCH YOUR SERVER SETTINGS
$DB_Host = 'localhost';
$DB_Name = 'Your_Database_Name';
$DB_User = 'Database_User_Name';
$DB_Password = 'Your_Database_Password';

// What Do You Want To Change?

$OldValue = 'star.jpg';
$NewValue = 'star.png';

// ** DONE EDITING ** //

// Connect to your WordPress database
$conn = mysqli_connect($DB_Host, $DB_User, $DB_Password, $DB_Name);

// Check connection
if (!$conn) {
  die("Connection failed: " . mysqli_connect_error());
}

// Escape the image filenames for safe SQL query usage
$old_image = mysqli_real_escape_string($conn, $OldValue);
$new_image = mysqli_real_escape_string($conn, $NewValue);

// Construct the update query
$sql = "UPDATE `your_table_name` SET `post_content` = REPLACE(`post_content`, '$old_image', '$new_image')";

// Execute the query
if (mysqli_query($conn, $sql)) {
  echo "Image URL updated successfully.";
} else {
  echo "Error updating image URL: " . mysqli_error($conn);
}

// Close the connection
mysqli_close($conn);

?>