E Imagin - https://baskmedia.jp/bp-e-imagin-35/
This'll show you where to find them, specifically the boards.

B Imagin - https://game8.jp/blue-protocol/521253
I suggest looking here for your choice of B imagin, once you're in, there's an area which tells you which enemy it drops from to collect the blueprint. Click on the respective name, it will give you the map local for where it will spawn for the specific enemy in question.