If I control both battlefields and I have a resonating strike hidden at the 2nd battlefield, am I able to move a unit from the 2nd battlefield to the 1st battlefield?

Yes. Playing Resonating Strike from Hidden at battlefield 2, you can choose battlefield 1 as the destination and a unit at battlefield 2 as the unit, then move it to battlefield 1.

The hidden-targeting restriction (Rule 811.1.d.2) forces the unit choice to be from the battlefield where the spell is hidden — here battlefield 2, which is exactly where your unit is. The destination just has to be a battlefield you control (Rule 449.1), and battlefield 1 qualifies. Since the unit must be "at a different location" than the chosen battlefield, battlefield 2 → battlefield 1 is the natural legal play; no Ganking is needed because this is an effect-based move, not a Standard Move.

Two notes: if you tried the reverse (unit on battlefield 1, moving to battlefield 2), that would also work via the "explicitly restricts targeting" exception, because no unit at the hidden battlefield could satisfy "at a different location" from battlefield 2. And because both battlefields are yours, the move applies no Contested and stages no Showdown. (Rule 811.1.d.2)