en_tn_condensed/rev/09/10.md

They had tails

The word "They" refers to the locusts.

with stingers like scorpions

"with stingers like scorpion stingers" or "with stingers that could cause terrible pain as scorpion stingers can"

in their tails they had power to harm people for five months

Possible meanings are 1) they had power for five months to harm people or 2) they could sting people and the people would be in pain for five months.