Passport diagnostic report "Windows has found errors on this drive"

Passport diagnostic report "Windows has found errors on this drive"

Worked perfectly last night. Has not been touched, moved, etc. since it was added. Now I see folders as they should be but each one claims to be empty when I try to open it. The drive is rated at 4TB and it currently has 3.1TB of data on it. I thought this was my most secure drive. I must find a way to save this data.