First, find herdiary.php:

Use your general knowledge and the hint on the tombstone to figure out that the underlined words in the diary correspond to the ten plauges of egypt. Find one word to represent each plague, this is a bit ambigious, as there could be many ways to name these plauges, but here are the correct ones (wikipedia seems to have different names for them, but many sources have these ones):

symptoms – boils
reptiles – frogs (actually amphibians but whatever)
swarming – locusts
pouring – hail
tears turning red – blood (when the river was turned to blood)
farm animals – livestock
biting – gnats
eldest son – firstborn
shadow – darkness
insects – flies

Preserve their order as given in the diary entry and use the n:th letter, as specified by the column of numbers in the original image, in each word.