Hide/Delete multiple workspaces created by a single user

Hi, 

I am fairly new to power BI and need some assistance. I have a colleague that was fired and was responsible for creating all the powerBI reports at my company. I have now created a new power BI account and I have started copying all the powerBI files over and I've created new workspaces that have the same name just with "new" at the end. Now, how do I delete/hide the fired colleagues old workspaces from those users that have viewer access, because they keep getting confused and look for reports in the old workspace. 

Thanks!