How many photons of red light of wavelength 700nm do you need to get at least as much energy as one of blue light with wavelength 301nm?

700/301 times. That is 3 photons ("at least" - more than two, less than three) - because a photon cannot be cut into pieces.
E=h*v
H is Planck's constant, v is the frequency (this is not the letter v but the Greek letter "nu").
The frequency is the speed (of light) divided by the wavelength.