IMac backup fails on WD My Book

WD External Drives External Drives for Mac
1

Unfortunately I can’t backup my files on “My Book”. The following error message is shown:

Time Machine couldn’t complete the backup on “My Book”: The backup disk is not in MAC OS Extended (Journaled) format, wich is required.

It would be grat if somebody could help me.
Best regards

2

Erase your external hard drive with MacOS Journaled and tryagain.