There is no real need to 'unmount' it. You just have to remove the card from the device.
Now, if it was encoded to run apps from it, removing it to use on another device (any device) won't work if you are wanting to move it with access to that data on it. Once converted to "Internal" storage and converted, it will only work in that one device.
However, if you didn't do that, and have just saved photos, music, etc., on it, you should be able to then just connect it to any other device and access the data.