Yes, i understood previously that you installed manually.
BUT, if you have cPanel and Softaculous you can import your current installation into Softaculous for better management. It is NOT a new installation, it is an import of the existing installation. Nothing will change, in your current installation. It just allows you to do more things, with less hassle.
If you have Softaculous in your cPanel, this will add the ability to change your admin password which is your current issue. It will also add the ability to clone or stage your existing site to test what is any issue you may have in updating your cart version or just testing out something new - all WITHOUT impacting your existing site.