My computers internal hard drive is not listed as a device in Ubuntu'

I need to know some things to start helping you:

1.) list the contents of the text file /etc/fstab
2.) list the results of typing ls /dev in a terminal

and how many drives are there and how are they attached to this computer?

-when I open the the file fstab, this is what is in there:

overlayfs / overlayfs rw 0 0
tmpfs /tmp tmpfs nosuid,nodev 0 0

-also when I enter "ls/dev" into the terminal and hit enter, I get the response: "No such file or directory"

-I really don't have any drivers attached to the computer... besides the internal hard drive or the external hard drive which I plug in to copy my files. I hope that answers your last question.

Thank you for your help in advance.

Are you running Ubuntu from a live cd?

also in that last command there should be a space between ls and /dev

At this point I'm guessing that you need to open your file manager as root and mount the device before you can read it.

try opening your terminal and typing (without the quotations) "sudo dolphin" and then navigate to /media to mount and see your drive.

Thank you for your help, but I don't know what happened but it just started working when I turned the computer back on... It works and I was able to copy everything from the hard drive.

Thanks again!