Switch between French and English keyboard layouts

The iPad User Guide is a rich (and often overlooked) source of information about your iPad and iPadOS. Here is a direct link to the relevant section of the Guide - that provides guidance as to adding and switching between additional language keyboards:

Add or change keyboards on iPad - Apple Support

and when you added more layouts you switch between them by clicking the globe on the onscreen keyboard

Go to settings… General… Keyboard… Keyboards… add French keyboard here.

Thanks for adding that…