The location of Let's Encrypt's certificates and other files are slightly different depending on your OS. For example, I use FreeBSD, so my files are located in /usr/local/etc/letsencrypt/. My understanding is that most Linux distros put them in /etc/letsencrypt/ (provided you're control panel uses the official client as the back-end). Different clients put files in different locations, so you'd have to check your control panel manual.
However you should first check to see if your question has already been answered here:
That's where I go for my Let's Encrypt answers. They've been asked similar questions to yours many times
Failing that, @kljhlkhglklfgh is correct, you should contact your hoster and read your control panel manual for more information.