Path to external drive docker/mac

Hi. Newbie question here.

I’ve installed docker on my mac mini and am running ownCloud. So far so good.

However, I want to enable an external usb drive as local storage.

ownCloud asks for a path to the external drive, but I can’t figure it out. I’ve tried:

/Volumes/drivename
/Volumes/drivename/
/dev/disk1s2
/dev/disk1s2/

None of them work. I’m still getting the red square meaning that ownCloud can’t connect to the disk.

I have verified that the disk is mounted on the mac, formatted and working properly.

Any suggestions! Thanks.