First, connect to the computer and backup your data.
If it is not severly damaged, there ar still chance you can get your data out.
Then change the internal HDD.
Buy 2.5' SATA drive based on here.
https://www.nextodi.com/drive-compatibility/nd2901/
Open up the back cover, than you will find 2.5' SATA drive.
Replace the drive and assemble the back cover.