The plural possessive form of the word ‘hero’ is ‘heroes’.
To explain further, when we talk about the plural form, we change ‘hero’ to ‘heroes’ by adding an ‘es’ at the end. This is common for words ending in ‘o’. Now, to make it possessive, we add an apostrophe after the ‘s’. Therefore, ‘heroes” indicates that something belongs to multiple heroes.
For example, if you want to say something that belongs to the heroes, you could write: ‘The heroes’ achievements were celebrated.’ In this sentence, ‘heroes” shows that the achievements belong to more than one hero.