Hi,
How could I connect Arduino pro mini 5v with a Xbee in breadboard.
Are you worried about the voltage difference between arduino (5V) and xbee (3.3v)? At a low baud rate (9600) you can just use resistor voltage divider to convert arduino output into 3.3V. Connect xbee output directly to arduino. It can read 3.3 as logic high.