What fittings do I need for fuel lines

[Groenys 57]

So I am trying to relocate the fuel tank to under the bed. My problem now is that I cant seem to get the right fittings for the fuel line. The couple auto parts stores here are no help at all. The only fitting they had was a male flare to go onto the stainless fuel line. I ordered 2 6an flare female by barb to connect the hard line to rubber line. The problem I am having is the fittings wont go together. I'm assuming the male fitting is correct because it fits on the stainless line, but the female fitting is to small to connect. I looked up and thought that 6an was 3/8? So my question is does anyone know the exact fittings I need for 3/8 stainless line? I have tried taking them in to the 2 parts stores around here and no one even has flare female fittings. Some pictures below of the fittings i currently have.

this is the male end on a piece of 3/8 line


this is the female by 3/8 barb end




this is them not going together. the male is to big.


I also don't know what the connection type is from my fuel pump. Can anyone tell from the picture?