If your external drive has been corrupted, you may be able to repair the filesystem by connecting to a PC or Mac computer - and allowing the computer to run its automatic repair tools upon connection.
Otherwise, it may be necessary to re-format the drive - which again requires access to a PC or Mac computer. Formatting will erase all stored files. Unless you have an alternative backup, you will lose any files that are stored on the drive. You should note that drive-formatting must be performed by a computer - as iOS/iPadOS has no capability to format external storage devices.
Before contemplating reformatting, be aware that there are commercial file recovery tools that can often recover much (if not all) files from a corrupted drive. Some recovery tools (e.g., Recuva) are freely available - but more sophisticated software tools usually require purchase of a licence.
When re-formatting the drive, you must use a supported format. Your iPad supports FAT, FAT32, exFAT (FAT64), APFS or HFS+ with a single partition. Microsoft NTFS and other proprietary formats are not supported.