The operation can’t be completed because the item "" is in use.

Try the steps in this Apple article:

https://support.apple.com/en-us/HT201583

I see 3 methods, which 2did you try?

Is Spotlight or Time Machine trying to use the drive?

EtreCheck is a simple little app to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac.

http://www.etresoft.com/etrecheck

Pastebin is a good place to paste the whole report...

https://pastebin.com/

Workable but harder for me to work with...the Note tool on the bottom of this editor's toolbar, as shown in the image, to copy and paste the output from EtreCheck.