How do I access a Memory Stick in Linux?

What does unix call the usb socket? Try 
ls -l /dev/disk/by-id
look for a file named something like usb-Ut163_USB2FlashStorage_000000000009... and note the name of the file it points to (e.g. ../../sdb1).

Next it needs to be mounted. If you are not root, it needs to be open to anyone to mount it. Look for device you can mount in /etc/fstab. E.g. 

grep user /etc/fstab
Hopefully this will show up something matching ../../sdb1 found in /dev/disk/by-id. Now mount it 
mount /dev/sdb1
Use ls, cp etc. on the second file name given in /etc/fstab. E.g. 
ls /mnt/usbdrive
cp -p /mnt/usbdrive/langdon_rnanet.pdf .

Remember to dismount it before unplugging if from the USB socket. E.g. 

umount /mnt/usbdrive

centos 7

For centos 7 the USB drive may be in 
/var/run/media/username

What USB devices do I have

Try 
lsusb
Based on
Created 28 Sep 2009 by W.Langdon (last update 12 Jun 2019).