How to see information from an external HD on raspberry?

Hi guys!

I like to check my Raspberry, but I´m only able to check the free space of my SD … I have SSD hooked, but i have no idea how to check the free space as well.

thank you in advance!

Checking the SSD info, I have the following: (the ssd is mounted on /mnt/SSD)
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I have tried the “/mnt/SSD” and also “/dev/sda”, but with no success … I get unavailable messages from both.
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