If your files originated from a mobile phone backup, they are almost certainly KeepSafe encrypted images. The Safest Way to Convert KSD to JPG
Search for specific converter tools related to the software that created the KSD file. ksd file to jpg converter
: Some versions of KeepSafe simply append a prefix to the file. Try renaming a copy of the file from KeepSafe Recovery Tools : KeepSafe offers a support center If your files originated from a mobile phone