Storage space

How can I see how much storage space I have used on my Wd MyCloud. I have a Macbook with Mac Os HighSierra 10.13.2.

log into the Dashboard and it will show you disk usage

https://support.wdc.com/knowledgebase/answer.aspx?ID=19545&s=

It is also possible one can use their OS file manager to see how much storage remains on their My Cloud device. For Windows one can use Windows File Manager. For Mac see if Mac Finder will indicate the storage amount used/free for the My Cloud.

I bought a WD My Cloud of 3 TB. On the dashboard I see a storage of 5.03 TB. Is it possible that this includes a connected external drive of 3 tb to the Nas?

Yes. Generally, if you have a USB drive attached AND have USB Content Availability enabled (set to On) in the My Cloud Dashboard > Settings > Cloud Access section, then the My Cloud will report the total free storage space of the My Cloud plus the attached USB drive.

Thanks, I do understand it now.