Seeing conflicting answers other places…trade in prep

If my MacBook turns on but doesn’t have an OS on it (because I deleted everything per their instructions), can I trade it in like that? I did everything listed to prep my MacBook for trade in, but can’t get it to reinstall the OS…says there is no location to install it to. Do I need to get someone to work on it at the Apple Store to install an OS before I can send it in, or is it ok as long as it turns on? It’s 7 years old, so not like they will likely resell it or refurbish it anyway…this is likely a recycle. Thanks