I am not even going to try and throw a number out there as it will be a lot but I will say you get 2-3 fists full of Blackworms (depending on hand size).
1lb is a lot. 1lb last me a month for my discus. and i feed my discus heavy 4-5 times a day. and whenever i rinse the worms some of them goes away. keep them chill or else they will only last like a few days or a week.
There are 16 portions usually in 1lb of worms and I would guess perhaps 700 worms per portion. Black worms are much smaller than earthworms and average 1" to a max of about 2.5" and are as thick as a large paper clip. Keep the worms chilled in a fridge (usually the lower part of the fridge) and rinse them out daily to keep them alive longer. If kept properly, you have keep them alive for a little more than a week if they last that long.
just remember to use chilled aged water. i use the waste water from my ro system, which stays fairly cold, and havent had any problems. my pound of worms barely lasts me until the next worm buy ~1month.