You need to tell us how you created the file or where you got it. In general, you use the application that created the file to open it. There are at least four known applications that use .LB file extensions, so we can’t know what will work without knowing what it is. Further, it could come from any number of other sources since anyone can use any extension for any personal purpose. Since it’s your file, you should be able to tell us what it’s used for. — Tom