I believe you are looking for VolumeLabel, try:
The label length is determined by the operating system. For example, NTFS allows a volume label to be up to 32 characters long. Note that null is a valid VolumeLabel.
foreach (DriveInfo drive in DriveInfo.GetDrives())
{
if (drive.DriveType == DriveType.Removable)
{
if (drive.IsReady)
cmbUSB.Items.Add(drive.Name + "-" + drive.VolumeLabel);
//^^^^^^^^^^^^^^^^
//here
}
}