That attenuator is intended for use in 50 Ohm systems, and is only rated at 0.5 watt.
Your 100 volt square wave will make it dissipate about 100 watts. although I suspect that the generator will not be capable of producing anything like that power.
You need a x10 scope probe, some are available with BNC adaptors for the tips, you just have to look for them.
Other than that, you could make a simple voltage divider.
But be aware that you will need to frequency compensate it if you want to see square edges on your pulses.
JimB