Sounds like you need a partition/data recovery tool like TestDisk (https://www.cgsecurity.org/wiki/TestDisk
Whether a data recovery tool like TestDisk will get your files back depends on the nature of the problem. If it is just a corrupted partition table, you should be able to get everything back. OTOH if the corruption is the result of malware/ransomware, or the drive is experiencing hardware issues, your mileage may vary (some or all of the files may be unrecoverable).
Depending on how important these files are to you, a professional data recovery service may also be an option. But be prepared to spend big bucks (typically hundreds of $).