For the bullet :https://www.scirra.com/manual/90/bullet :Set speed
Set the bullet's current movement speed, in pixels per second.
for custom movement :https://www.scirra.com/manual/92/custom-movement :Set speed
Set the current speed in pixels per second either for the horizontal or vertical axes, or the overall movement speed. Setting horizontal or vertical speeds assigns dx and dy directly. Setting the overall speed calculates new values for dx and dy such that they reflect the new overall speed while keeping the same angle of motion.
This only took a few seconds to find !!!!!!!!!