Does apple AirPort extreme has a internal hard-disk to backup my apple devies

No. However, the very similar looking Apple Time Capsules do. In addition, it is possible to attach an external USB drive to the Extreme to use for backups.

There are three basic steps required:

1. Obtain an external USB hard drive and attach it to the USB port on the AirPort Extreme base station.
2. Format the drive as HFS+ (aka, MacOS Extended Journaled) using the Disk Utility.
3. Configure Time Machine to use this drive.

Ref:

• Backup disks you can use with Time Machine - Apple Support
• Back up your Mac with Time Machine - Apple Support
• How to use Time Machine on your Mac - iMore