Are you referring to this https://docs.joomla.org/J3.x:Privacy#Short_Privacy_Policy

referring to Content - Confirm Consent
Privacy Note * is in it near required checkbox to a form eg the core contact form.

For the default Short Privacy Policy.
The default string should be translated.
For example in French we have in administrator/language/fr-FR/fr-FR.plg_content_confirmconsent.ini
PLG_CONTENT_CONFIRMCONSENT_FIELD_NOTE_DEFAULT="En soumettant ce formulaire, vous acceptez la politique de confidentialité de ce site Web et le stockage des informations soumises."

If you want to modify the default text, you have 2 solutions:

1. Via language overrides, create as many overrides as languages for that constant.
2. Also a solution is to enter in the default field a new constant and then create the string via Languages Overrides.

result:

For the full policy
Select a Privacy article containing whatever you want in the language of your choice.
If your site is set as multilingual, you can associate the articles concerned so that will be presented the article in the language of the frontend.

The problem is in near required checkbox to a form eg the core contact form.

What you done to make it change from Privacy Note * to Note de confidentialite* ?

How you managed to modify this text Privacy Note*

The string for that is
PLG_CONTENT_CONFIRMCONSENT_CONSENTBOX_LABEL

If you want to modify it, you may (same method as used above) use a language override in the site part of the language.

As this type of question should have been posted on the forum, I am now closing this issue.