Connecting to Private Network via OTAA

I suppose that is a private LoRAWAN network.
What is the format and size of the application EUI and application key?

Application EUI has to be a 8 hexadecimal values, if You have a shorter one than You need to add "00" at the beginning.
For example "00AABBCCDDEEFFAA"

Application key is 16 hexadecimals.