Hi @RobertH, and welcome to the Shotgun community.
The Shotgun web application never removes any media. When you send something to the trash, we mark it as retired, but don’t delete it should you want to move it out of the trash. In the case of archived projects, that’s even less “destructive” than the trash as it just marks the project, and any data from archived projects are then excluded from searches by default.
Based on your question, I’m going to assume your Shotgun is locally installed on-prem and not hosted. If that is the case, you’ve got a lot more latitude towards managing your media than a hosted solution that we manage (and you probably don’t have to worry about media space on hosted).
If my assumption is correct, this reply should help you understand the pattern of paths where media is stored.
Let me know if my assumption was wrong or if you have additional questions.