What you're seeing with the .vmwarevm folders is normal behavior.
Installing Fusion makes macOS recognize folders having a .vmwarevm extension as "virtual machine bundles" and makes them opaque to the Finder. It also changes their file lkind to "VMBundle"
It's also normal that when Fusion is installed, when you want to examine the contents inside of the bundle with the Finder, you right click on it and select "Show Package Contents".
Note if you went to the command line, this "hiding" doesn't occur. The virtual machine .vmwarevm folder is still treated like a folder.
First, is there a .vmx file in that virtual machine .vmwarevm bundle folder, along with the other files?
"Open existing" doesn't appear in the Fusion menus to open an existing virtual machine. You should just be able to open the virtual machine with "File > Open" and then navigate to the folder containing the virtual machine .vmwarevm bundle - the Finder may not show the extension, but will note it as a file kind of VMBundle. Selecting the virtual machine bundle should open the virtual machine and add it to the Virtual Machine Library.
Unlike VMware Workstation, you do not navigate to find the .vmx file for an exiting VM. Fusion will look for it in the VMBundle that you select in the Open dialog.
This assumes that you have file permissions to access the VM.
Can you tell us exactly what sequence of commands that you are using (perhaps with a screen shot). Something is amiss here.