Convert String (5-byte HEX) received via Serial to uint64 for nRF24L01+ address?

[system]

From the example that comes with the RF24 library...

const uint64_t pipes[2] = { 0xF0F0F0F0E1LL, 0xF0F0F0F0D2LL };

or in your case

const uint64_t pipe = 0xb3b3b3b3b3LL);