cgsecurity.org

Hope this is not off topic

I downloaded testdisk both 7.1 and 7.2

It is a zip file of size 21kb

I tried to open it but it said The archive is either in unknown format or damaged

Download from here:
https://www.cgsecurity.org/wiki/TestDisk_Download

The Win64 version is 26 MB.
Ensure that you have enough space at your download target location.

Unfortunately you neither wrote where you downloaded Testdisk from nor which file you downloaded.