Search after a number pattern

I'm new to this. I just copied my frist script to "tampermonkey".

Im trying to find a pattern of numbers on a website like 500500, 600600, 707070, and similar.

I have this code:

$(document).ready(function() 
{
    var LookFor = "test"; // Change this to find a different string

    if($('body:contains("' + LookFor + '")').length > 0) 
    {
        alert("Found: " + LookFor);
    }
    else
    {
        location.reload();
    }
});

But I dont know how to search after patterns. I would appreciate if you could help me out.