Can I use a Hidden Wages of Pain on an enemy at a different battlefield?

No, you cannot.

According to Rule 811.1.d.2, if a spell played from Hidden chooses any targets, those targets must be chosen from among options at the same battlefield where that card was hidden.

Because Wages of Pain requires you to choose a target ("Deal 3 to a unit at a battlefield"), you are strictly limited to targeting units located at the specific battlefield where you hid the card. You cannot use it to target a unit at a different battlefield.