I want to back up my photos in their current folders and albums onto an external hard drive. Does anyone know the best way?

Hi

In my opinion the best way to back up data from your mac is time machine.

Back up your Mac with Time Machine – Apple Support (UK)

Alternatively you can move or copy the whole library to a properly prepared external drive:

See

Move your Photos library to save space on your Mac – Apple Support (UK)

Pay particular attention to the format of the drive, setting the ignore ownership flag, and making sure it is a locally connected drive (no Ethernet, no Wi-Fi)