iCloud is pushed by apple to create or store backup on iCloud but to backup data more than the size of your cloud you must need to buy the plan of iCloud storage to backup whole Mac. The only way to get rid of this purchase is to backup data into an external hard drive or you Apple is sending you a warning about backup or data will be gone as the hard drive may not work for a long time.
If you want to create backup or want to restore an existing backup read to know best methods on How to Backup and Restore Using Time Machine. But to create backup of Mac from external hard drive you need to follow below steps and user needs to execute all the methods step by step to solve the issue.
METHOD1: FORMAT EXTERNAL DRIVE
Step1: Connect external drive to Mac and open disk utilities located in the application.
Step2: Select your hard drive from the volumes listed in the Mac.
Step3: Press erase button and rename the external drive connected.
Step4: Select a mapping scheme used to store and manage your data in external drive.
Step5: In security options select override data at least by 3 times and confirm format option.
METHOD2: USE TIME MACHINE
Step1: Open time machine and click on system preferences in time machine.
Step2: Toggle the switch located in time machine and select external hard drive.
Step3: Set password and click options button to start automatically backup of data.
METHOD3: BACKUP COMPLETE DRIVE
Step1: Open internal drive of Mac and open all the drives.
Step2: Copy all the files located in the drive and drag to drop in open external drive.
Step3: Complete step1 and step2 of method3 for all the drive partitions created in internal drive for Mac.
The right procedure to create backup in external hard drive is explained by experts and listed in the blog above to transferring files from Mac to pc external hard drive. If you need instant assistance online you need to call +1-888-488-2930 (Toll-free)round the clock for help from certified technical professionals of Mac customer support number.