I'll know it
I'll know tomorrow.
Si elles ne sont pas les bonnes, je le saurai.
If they’re not the right ones, I’ll know.
— Star Trek Into Darkness (2013)
I will know.
Je ne sais pas encore où, mais je vous le dirai dès que je le saurai.
I don’t know where yet, but I’ll let you know as soon as I do.
— The Mask (1994)
I will know soon.
How will I know?
Je vous le dirai quand je le saurai.
I'll tell you when I know.