Your flash drive is sdb and only one of 2 partitions on sdb is mounted, sdb2 on /media/john/usbdata. The first partition on sdb, sdb1 is not mounted and contains an iso file system. If you want to read what is on sdb2, then run sudo chmod -R 777 /media/john/usbdata/ as suggested above and see if you can enter and read what's on /media/john/usbdata.

did you open gparted to ensure it is only one partition?
is it ntfs or any windows ?

got ntfs-3 installed?

their is another format that needs to be installed Sometimes -- xfit ( I forget) something strange thing like that. But that has to do with Android phone formatting

a file manager ( mine does) just mounts all mountable partitions on whatever I plug into it. But someone said FenDora is not good for .. doing that.

you should not even have to manually mount it. but if that is how fendoria rooolllssss - I'm happy I not use it.

Reread the prior posts. From the lsblk and mount output there are two partitions on the drive. The first one has an iso file system, probably from someone using the dd command to transfer an iso file to the first partition. The second partition is formatted ext4.

just a check off list:

Well, I thank everyone for their valiant efforts here, but I'm left feeling as confused as ever. I do not, nor have I ever, used Fedora. I'm not sure where that came from. I use Xubuntu and before that I used Ubuntu. The friend who sent me the flash drive uses Slackware and I know he's only used Slackware for a long time. What I gather from the above is that there are two partitions on the drive, but thus far neither of them opens. I tried running sudo chmod -R 777 /media/john/usbdata/ as suggested and I still cannot access anything. One difference it made was eliminating the "x" that was over the usbdata folder. Even so the folder does not open. A flash drive is a small device. Maybe the simplest thing would be to just send it back to my friend and let him make whatever adjustments (or replacements) need to be made.

Unless there are any additional suggestions at this point. I really do appreciate this thoroughly knowledgeable and very helpful input!

Do you know what type of data your friend was trying to send you. The reason I ask is the lsblk output you posted makes it pretty clear that your friend sent you a flash drive that was used to make a bootable flash drive for installing Debian Jessie. If that's not what he was suppose to send you, then he probably inadvertently sent you the wrong flash drive.

I thought it was an installation for the latest update of Xubuntu, but I know he was suggesting Debian. So if this was strictly an installation drive it wouldn't respond to attempts to "open" it? My understanding was he was going to include a lot of additional information besides. But now I'm wondering if maybe it was just the bootable version of Debian.

I would try booting off the drive and see if you wind up in a livecd environment. If that happens, you can probably access the extra data your friend sent from within that environment.

What would be the process for doing that? Since my computer already has an OS installed how do I signal to the computer I want it to boot from the flash drive? If I have the drive plugged into a usb port, what happens after I push the power switch? (This is actually a good idea, incidentally!)

Okay...I did kilgoretrout's suggestion and booted from the usb drive. It did work...I got into Debian 8. Very limited use, however. Is it possible to get on the internet through a live boot? I was unable to do so. I think this is all that was on the drive. I tried mounting the drive while in Debian but still nothing resembling data.

Debian has some support for internet by default on live. Since you claim not to have it we have to assume either you need driver or configure the network as two most common I'd think. Some distro's ship network disabled by default. Debian usually is on if who ever made it as normal install.

It's certainly possible but as suggested above, you may not have the driver(s) necessary for your hardware. Since the Debian is "Live" installation, it is read-only by design and if you were to be able to obtain and install the proper driver, it would have to be done every time you reboot the "Live" install as everything is lost on reboot.

Perhaps if you posted how you tried to access/mount the second partition, someone might have a suggestion.

Sure. I didn't have to do anything, really. I had the usb drive inserted and as the computer was booting up, I held down F12 to get into the BIOS. At that point I was asked which drive I wanted to launch and I took the cursor down to usb Debian. And it just came up. I went into the Network manager and they wanted the Network name, SSID number,and that did nothing. From what I understand, the internet capacity should be available as soon as the live boot comes up.