Your best bet at this point, unless you have some sort of viable backup you can recover is to search the internet for a decryptor tool. Based on what evidence the ransomware left behind you may be able to determine what variant was used. Various "good guys" out there have succeeded in breaking a number of encryption keys used by ransomware, and make them freely available to victims. Again, research the internet- here is a site to check to get you started:
https://www.thewindowsclub.com/list-ransomware-decryptor-tools
There are also forensic data recovery folks that may be able to recover some of it, but the only guarantee there is that they won't be cheap.
If the data lost is irreplaceable and extremely valuable, you may even consider paying the ransom. Some (but not all) of the "bad guys" actually do supply keys that work.
Good luck, and don't get your hopes up too high, once they get in the door, the "bad guys" have (almost) all the advantages in the malware game.
