How do you reuse old launcher Custom packs

[Eegxeta]

I made a custom pack on the old launcher I have all the files for it and all. I want to use it on the new launcher, but I'm not sure what kind of changes I'm going to have to make to the files.

The thought just occurred, does anyone know how to make java assign a block a unused id to a block if there is a conflict because it would make life easier.

[Eegxeta]

Nevermind I worked it all out.