i want to share a private pack i made whit a friend but i don't know how.
Private like in not publicly available? Then unfortunately I think this is not possible.
You could however go to your modpack folder and copy the mods and config folder, and give it to your friends.
The other alternative is to just upload it to curseforge, it's easier, but then it's publicly available.
Can you private your own public mod packs?