Hi all, I am using Mazzer mini manual grinder I use to set around number 3ish, now I am trying to grind for french press coffee, any idea of approximately what number should I dial in?

Thanks in advance

You will not be able to get an good french press grind from the Mazzer mini... It is an espresso grinder and that is the opposite end of the spectrum, when compared to French press.
It has been awhile since I have owned a mini but you might be able to get as high as a drip setting and nothing past that (it will not be very suitable for even this though). There is good reason we recommend two grinders in this situation, one for espresso and the other for brew.

And it just makes it a pain to dial in espresso.