The No More Ransom project website has free decryption tools for many known ransomware types.

The United States Cybersecurity & Infrastructure Security Agency (CISA) has a site with tips on how to prevent ransomware attacks.

If a decryption tool is not found, one option is to replace the hard drive and operating system and save the locked drive offline. A decryption tool may become available months later to free the data at that point.