I highly recommend if building a nest box you also provide live food for your birds. Otherwise many chicks will likely not survive. Live feed is important because of its high water content. You could re-hydrate dried worms, however most dried worms are microwaved so are in fact hollow! Hollow things dont absorb water well. Genuine freeze dried worms would be better as they aren’t hollow, however they are a lot more expensive. Confirm with the supplier if they are genuine freeze dried before buying if you want to go down the re-hydration route.

I buy mine buy mine from https://www.livefoodsdirect.co.uk/ and I select the mini meal worms for the first 10 days or so, which are small enough for the hatchlings. In the 21 days they consume between 250-750 grams. Closer to 750 grams this year with 8 chicks and the robins visiting. Below is what 250 grams of mini worms looks like.

I empty the worms into a plastic tub or two, and feed them with carrot and potato.