Is this the same drive you were using on Zorin OS 16? It looks like it's not formatted, which would explain why it's not showing up anywhere else since the OS cannot actually use it even though it's aware of its existence.
Before you format anything make sure to make backup copies of whatever is in that drive, as the contents will be overwritten. Once you are sure of that, click on the little + icon and create a new partition. Take a look at this post for more details: