ipad 5 will not connect to iphone SE via bluetooth

Whilst it is technically possible to “pair” iPhone and iPad via Bluetooth, the connection does not support file transfer between devices.

Perhaps the best methods of transferring files and data between iPhone and iPad, if access to iCloud is unavailable, is to consider either AirDrop - or use of an external storage device such as a USB Thumb Drive via an USB appropriate adapter.

AirDrop

How to use AirDrop on your iPhone, iPad or iPod touch – Apple Support

https://www.imore.com/airdrop

USB Adapter

Lightning to USB 3 Camera Adapter:

https://store.apple.com/uk/xc/product/MK0W2ZM/A

for what purpose?

they can't sync or share files or the likes with each other