Your iPad will not be able to access an SSD after being encrypting with Sandisk-proprietary security software. An equivalent App is not available for iOS/iPadOS.
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 and other proprietary device formatting are not supported. iOS/iPadOS does not natively support encrypted volumes.
Be aware that iPad does not provide any facilities to format an external storage device; formatting, of required must be performed by a suitable computer. Note that FAT filesystems are typically universal - while APFS and HFS+ are generally only usable with Apple devices.
More information about connection to external devices and storage can be found in the iPad User Guide - along with other frequently overlooked information about your iPad and iPadOS:
Connect external storage devices to iPad - Apple Support
If you are looking to accessibly encrypt your SSD data, you’ll need to find an encryption software solution that is available for all devices with which you intend to use your SSD. You might consider Cryptomator 2 - this being available for both Mac and iOS/iPadOS:
https://cryptomator.org/downloads/
https://apps.apple.com/gb/app/cryptomator-2/id1560822163
Cryptomator does not use full disk encryption, but instead employs encrypted containers - these being created and accessed using an appropriate client App that integrates with the native file viewer.
