I completely forgot the password and e-mail to the site I am an admin of

Hi guys.

This might seem like a repetitive question, but how on Earth do I reset the password to a site I edit constantly, even if I don’t know the retrieval e-mail? To make a long story short, the website is for a family business. When I still lived with the parents, I edited the website regularly. However, when I moved away for college, I changed laptops, then basically forgot everything I had to know to access the admin account. It’s been three years since the last update. Version 3.6.1. I just need fast answers because I won’t be able to sleep until I figure it out (yeah, I’m like that).

Cheers,
Dei