Facebook is a very large community where millions of users stay active daily. So, it can be very hard to find someone on Facebook. So the best way to find someone is with their username, if you also do not have someone’s username then you should find them with their phone number.
If you have someone’s phone number then find them by the following methods. Enter the phone number in the search bar of Facebook and then enter. If you have better luck then the person is finding will show up in the result. Choose the person from the results given on the screen.