Never format a drive that contains data you want to keep. Permissions are almost always reversible. Formatting is not.
Sometimes a conflict in drive letter assignments causes this error. External Hard Drive Access Denied - Microsoft Q&A external hard drive access denied
This error indicates that Windows recognizes the drive, but a security or file system issue is blocking your entry. Whether caused by improper ejection, corrupted file permissions, or a sudden system update, this issue is usually fixable without data loss. Never format a drive that contains data you want to keep
Troubleshooting Guide: External Hard Drive "Access Denied" Error corrupted file permissions