You click Turn off reminders but the message appears the next time.
Now, this post fromMiniToolprovides ways for you to suspend the Windows 10 backup notification.
Is there any way to disable Windows 10 backup notification permanently?

The answer is Yes!
delete-old-windows-10-file-history-backup
Method 1: Via Control Panel
How to disable backup notification from taskbar?
you’re able to do this task via Control Panel.

Step 1: TypeControl Panelin the Search box and click it to open it.
Step 2: Go toSecurity and Maintenance > Change Security and Maintainance options.
Step 3: Under theMaintenance meesagespart, uncheck theWindows Backupbox and clickOK.

Then, name itExplorer.
Next, name itDisableNotificationCenter.
Step 4: Double-click theDisableNotificationCentervalue and change its value data to1.

Step 1: Press theWindows + Rkeys together to open theRunbox.
Typegpedit.mscin it and clickOKto openLocal Group Policy.
Step 2: Navigate toUser Configuration>Administrative Templates>Start Menu and Taskbar.
Then, in the right panel, find and double-clickRemove Notifications and Action Center.
Step 3: In the Remove Notifications and Action Center window,checkEnabledand clickOK>Apply.
Restart Windows 10 to make changes take effect.
Its a professional backup and sync tool with a simple interface.
You wont receive any notification when you are working.
In addition, you’re free to set automatic backup tasks with it.
you’ve got the option to try them one by one.
Besides, there is another backup tool for you that wont bother you.