Powering the external USB drive means it’s less likely to come corrupted (or knocked onto read-only mode) due to lack of power. So if you’re looking to continue using this device, externally powering the USB drive would be a good idea.
If you’re asking if you have to replace your SSD, no, the suggestions you’ve been given have been to power the drive you already have.
A popular option is this kit that Start9 used to provide…