On a Medium Super plasticell foundation I have 27x78.5 x 2 sides = 4238 cells, of course they would all never be 100% brood to emerged bees. Likewise, with the bees in a pound, if they just fed them, and they were younger FAT BEES to start with, they will weigh more than old, starved forager bees, but going with 100mg per worker bee and forgetting about 200mg Drones or Queens, a Pound being 455.592 gram, means you get 4536 Worker Bees per pound (U.S. Lbs), say 4500 more or less (and it is always going to be less bees by the time you get them....they may be well fed and well sprayed with sugar syrup going into a package, but by the time they travel, and are not as well fed, and dry, well, they lost some weight on the TRAVEL DIET, so 3Lbs will no longer be 3 Lbs, but the bees minus the dead dozens enroute will be the same number of bees as when weighed....so my guess is, 3,000 is way too few, 3500 is a good approx., but you will never get 4500, and would be lucky to get 4,000 where a 3 Lbs package would be 12,000 bees to under 13,500 bees for sure. For every Drone, you have 'one" bee, but at the weight of "two workers", so you are really losing there, when you figure in Drones as a percent, since they do not work....unless you need to get a virgin queen mated in a hurry. You can figure a Pound (1 Lbs) of bees would cover 2 to 3 medium super frames, I use plasticell myself, 27X78.5 x 2 sides is 4238 cells, but your 4,000 to 4500 Pound (US 1 Lbs) 0f worker bees are not "in" the cells as brood, they are moving around, shoving, and pushing and running, and doing their thing, so they have that "personal boundry" buffer space going on, so figure about 2 to 3 frames of coverage, so tha a 3 lbs of bees covers about 8 frames, just enough to qualify usually at the minimum standard for Almond pollination.
If you still are masochistic or old fashion enough to use the heavier DEEP HIVE BODY then multiply all the above numbers by 1.5 since there are approximately 3 medium supers (6 5/8th) equivalent to 2 deep brood boxes (9 1/2 inch) or 2/3rds one way or 1.5 the other way (3/2=1.5) .... enjoy.
If you want to learn more, I plan to do videos later this summer and fall at
http://www.LorgeHoney.com or you can emal me at
Lorge@LorgeHoney.com