I am looking for a good flash drive for my iPad Air 12 ios

To be recognised by iPadOS, the attached USB storage device must be formatted to FAT, FAT32, exFAT or APFS with a single partition. As the iPad has limited power capabilities, dependent upon the Storage Device, an external power source is usually required.

If your iPad Pro has a Lightning port, you will need to use an Apple Lightning to USB3 Camera Adapter to directly connect USB devices to the iPad. This adapter has both a USB 3.0 Type-A connector and an additional Lightning port to supply power, from your charger, to both the iPad and connected device. The external charger must be rated at 12W or more.

For your first generation iPad Air, choose a simple Flash Storage device from a good quality brand - and not an SSD that uses write-caching.

Some additional information can be found here:

Connect external devices or servers with Files on iPhone - Apple Support

https://www.imore.com/how-use-external-hard-drives-your-iphone-or-ipad