Do you mean the menu entry for the enemy guide? It's in one of the scripts called "モンスター図鑑", 12 down from "◆KGC software<1/2>". There's a variable called VOCAB_MENU_ENEMY_GUIDE which defines the name for the menu entry.
Or if you mean the actual enemy descriptions, then they're in the notes for each enemy. Be careful what you translate in the notes though, some of it is parsed by scripts
I translated Rise Senki Sinamonica, Arumero Soft's previous game, and this game seems to have inherited a fair amount of work from that game. I'd love to help translate this game too (though I don't actually know any japanese), but unfortunately I will be gone on vacation for a month. Maybe I can help with something when I get back, we'll see.