Need to clean out mysql - id valid/active from invalid/inactive to delete

Novice here, maybe a simple set of tasks? Hope someone can help. A support team trying to install Drupal 8 for three sites I run has installed multiple dbases, some named Drpl### others a variation of the website domain name, with 3-8 for each (!) domain. I want to get rid of the erroneous and inactive dbases, but am fearful of destroying the active sites. Then, I can backup to perform upgrades safely. How can I tell what's active and what's not? How should I tackle the challenge? Thx for any advice! JJ