Without benefit of a screenshot, contributors here have little idea of precisely what you see. Perhaps you are attempting to format or otherwise prepare the SSD while it is connected to a Mac computer or Windows PC?
To be recognised by iPadOS, the attached USB storage device must be formatted to FAT, FAT32, exFAT, APFS or HFS+ with a single partition. Microsoft NTFS is not supported.
If connected to your iPad, you can format the drive directly from the Files App. From the Files App sidebar, you should see the USB device; to format, touch-and-hold the associated icon, the select Erase from the Action Menu.