16Gb USB drive

I have a 16Gb USB drive and have some data stored on it. The drive has very limited free disk space left. I was trying to download a file from DELL yesterday to that drive. The download failed because of the drive is out of space.I guess I must have maxed out the disk.

Then, the system could not recognize this disk, keeps asking me to partition/ format this disk.

Any tools/utilities I can use to restore the disk partition and access the data I had saved there ? Thanks.