How to Recover the files in MY Vault?

I deleted some important files carelessly in Secure Access 2.0 (MY Vault) of a Sandisk 16GB USB, after that I try to use the Recovery Software(EaseUS Data Recovery ) to scan the USB , find some .dat file in the USB by EaseUS, the orginal files  seems like encrypted to be .dat file, Any solution can decrypt these files to restore the orginal files?Thanks~!!!