The easiest way to backup your photos is to use a Sync Tool.
1 USB External Hard Drive
Step 1) Download and Install the Free File Sync backup software
Step 2) Connect the USB External Hard Drive to the computer
Step 3) Choose your Photos folder in the left pane
Step 4) Choose the USB External Hard Drive on the right pane
Step 5) Click on the Synchronization Settings on the right. Choose the settings as shown below.
This backup profile creates a copy of the photos folder on the USB external hard drive. If a file is deleted from the source, it is NOT deleted on the external. This is so that, if you accidentally deleted a photo from the source, it will still be available on the external backup.
Step 6) Click Compare
Step 6) Click Synchronize