Here is a better answer than my first one.
Amazon will provide a free and excellent Oxford Hachette French to English dictionary, but only (if I remember correctly) if you click on a French word on a kindle set to the English language.
If you set your kindle language to French, then click on a word in a French dictionary, it will download a modern French dictionary.
Here is my dictionary list, all free, apart from the top one, which I am borrowing through my Kindle Unlimited trial, but it’s only $1.99, so I’ll probably splash out when the trial ends.