Decrypt files recovered from encrypted external hard drive

I am trying to recover the data from one of the external hard drives of my company. I ended up using DiskDrill to extract all the files into a new, non-encrypted hard drive. Unfortunately I made the mistake of erasing the original hard drive before properly checking the exported data… :/

If I look at the recovered data, all the file structures and file sizes seem correct. But if I try to open any file I get a system error saying:

"The document “File.rtf” could not be opened."

I used cat to check the content of the file, and from the outcome it looks to me like it's still encrypted:

|?!?z?n;?AԒ??Ћ???f??Y?-?bA?-??ۚw?5?vc?D???yr????l?&yg?????U#
????F?????l??
??ٔ=??S?????#t????v:??#?˰wDZ$??y>?n??y??C?j??,???WI?L?[?a??CC?
P?U?>K?l?Ե???????OH?[Ẉ[Y?'^k?*?mDћ)?,0?Ի;
??^?\dW?|?`??=?c6&-~?\?YT+3w?4d?'?F@???D???G(?$??>??+?҃?6?t????p?M?wC[?:?$d1?{?Ϊ?.???~KW?r??Q?6??
o@???u???
?B|?[[??>/%???$??[;?z?h?!???O??dn??;?"?GZ?v?{W?B???[???P?d?!????d??Q?@?mG??/?|?x?_???H%)?v?Z??$?]????F??>?"????!U?rFl???
?GB2?W0Iy??]??|x??]X??aN[??????WJ??????l B??噡g?ہ'I???^}Yk>??Ǘ

The command:

file -  /Users/Cortana/Desktop/File.rtf

Returns:

application/octet-stream; charset=binary

The original disk was encrypted using FileVault. I do know the original password.

Is there any command I can run in terminal (or anything else really) that I can do to recover my data. I'm not an expert at unix so please explain it to me like I'm 5.

Thank you,
Danny