We need to be able to edit those areas of the website which has super admin access only. The current listed members of super admin'ers who were from our previous hosting company no longer support us as the hosting company closed down and we moved to a new hosting company. We can only edit to 'staff' level of approval which for 90% of the content is fine but ultimately limiting. How can we regain full control of the website?
I wouldn't recommend changing the hash function to MD5 as it has been insecure since 1996 (no offense Jelle). What I would recommend doing is changing the email to a Super Admin row in that table to an email you have access to, then using the reset password functionality in EE. From there, you can reset that users password safely and go about cleaning up your Super Admin members however you see fit.
As long as you have database access you're good. If you go into the database (with phpmyadmin or simiar) you can find the exp_members table. in this table find a super admins's record. choose to change this record: type in a new password and set the function to MD5 and click save. This should give you a reset password