For an unmanned probe which can theoretically withstand 100G acceleration, from Lunar orbit, in regards to Project Orion.
Is that possible at all? Given the relatively low accuracy of all estimates, 1% or 10% of the speed of light would experience only minor relativistic effects. I will therefore treat them as 3.000.000 m/s and 30.000.000 m/srespectively. Given those extreme velocities, the fact that you start in lunar orbit is not important. Also, the exact number of pulse units is highly dependent on the payload mass and the implementation of the system.
The paper on project Orion state a maximum ISP of 1.3 * 10⁶ s. Plugging this, and the target velocity into the inverse rocket equation, gives a mass ratio of 10 for the 1% of speed of light spacecraft, and aprox. 10 billions for the 10% spacecraft.
But, the paper also gives ISP values several orders of magnitudes lower for any actual implementation of a nuclear pulse rocket. So fractions of the speed of light are even inaccessible for the Orion.
Of course this is hard to estimate accurately, but a few percent of the speed of light is achievable. The actual number of pulse units is more difficult to answer, as their decided size is a bit arbitrary. As bigger nuclear charges are more effective, I choose pulse units giving your stated 100g of acceleration. Then the number is around 10000 for 1% of the speed of light.