Oh, dude, it's like this - so, Mercury peroxide is called that because of the way the atoms are all cozy together in the compound. It's like Mercury (Hg) is hanging out with two oxygen (O) atoms, so they're like, "Hey, let's be peroxide buddies." It's all about chemistry vibes, man.
This formula, if the compound exists, is the formula for mercury(I) peroxide. The formula for mercury(II) peroxide would be HgO2.
The formula for mercurous peroxide is Hg2O2.
Mercurous has a charge of +2, and Oxide has a charge of -2. You cross the chargesand get Hg2O2. The 2s cancel out, leaving you : HgOnuh uh, mercurOUS has a charge of +1, so it's Hg2OmercurIC has a charge of +2, that would be HgO