Hint: Peroxide linkage is generally found in oxoacids with higher oxidation states calculated.
Consider the highest oxidation state of Sulphur which is +6. Calculate the oxidation states of Sulphur atoms using the normal calculation method. If the oxidation state is equal to the highest, there is S−O−S linkage.
For example oleum. If the oxidation state calculated is lower than highest, there is S−S linkage for example H2S2O4 or H2S2O6. If it is more than the highest possible, there is peroxide linkage, i.e. S−O−O−S linkage such as H2S2O8.