Programs enabling conversion of the file:
If your objective is to convert the file from JP2 to the file ICO, you can use any of the applications listed. JP2 to ICO conversion process in every program intended for this purpose (so-called converters) is very intuitive and everyone is able to manage converting a file.
However, bear in mind that the list may also include programs to support and work with the indicated extensions JP2 and ICO - and not only converters. In such a case, you need to open the source file JP2 and from the options available in the program, choose ”Save as... ICO" or "Export to ICO".