how do you attach a board to a maker pipe? I am making an electric scooter partially using these and i need to know how to attach it to the deck

Go to the hardware store (electrical dept) and ask the guy to show you ALL of the ways to secure EMT to a wall.  They have dozens of different kinds of clamps, straps, brackets, that ALL are made to hold EMT (conduit) onto something.. but they'll easily work the opposite way (to hold something ON to EMT) :-)

Your best bet is what Dommy G said to consult the electric department. Another option that would be lighter is to use self-tapping screws through the board into the conduit. You would need to make sure you line everything up perfectly, but in the long run, you may save a decent amount of weight on electrical fittings, which may or may not be important for your e-scooter build. I would personally use one-hole or two-hole conduit straps for ease of install.