can i have the bin flash file for microtik 750 gr3 to program it by my mini pro?
bin bios file is absolutely different , you can't do that , it should be the bios bootable file.There is no such thing published by Mikrotik.
If you want, you can download NPK and unpack it (Not that hard - all tools were made public by security researches over year ago. If you can't, don't really bother with anything else). Once unpacked, you can go through files and identify the one which you would describe as "bios". (I am not aware of anything like that. Closest file is "firmware" which can be found in /etc folder)