How do I see a hard drive attached to my laptop?
Your profile indicates that you have an iPad Pro. When you say "laptop", are you calling your iPad Pro a laptop?
If not, what laptop do you have? A Mac? A PC?
I have downloaded information from my computer to an external mobile hard drive
What kind of computer do you have? A Mac? A PC? Should we assume that the hard drive was connected to your computer using a USB cable?
And I attached it to my computer how do I see the attached or table hard drive?
In the previous sentence, you just told us that you downloaded information from your computer to the mobile hard drive. In order to do this, you would have had to have seen the mobile hard drive using the Finder on a Mac or File Explorer on a PC in order to download information to the device.
So, looking through the information that you have provided, we are confused and will need some more details to understand what devices you are using and what you are trying to say.