Help! Still new to MacBook. Trying to backup and move files to a new external hard drive. I have MacOS Mojave. Version 10.14.5 MacBook Pro 13" 2017
The Hard Drive is SP Armor A80. It keeps popping up
"Time Machine could not create a local snapshot to backup from because there was insufficient free space on the source volumes."
I don't know what this means or what to do???