I need to know what the part name is and where exactly to buy these at

I am replacing my.radiator and i need to buy a transmission line that goes to the radiator i guess but i cant find where to buy one at? Do you know what the part is exactly called and where to buy it at and how much? Also i need to know does it matter what kind of coolant i use to put back in my new radiator once i replace it with the new one can i just buy the dollar general cheaper coolant or does it need to be a certain kind or brand andhow many jugs of it do i need to buy?