The conjugate acid of H2S is H3S+.
To understand this, we first need to know what a conjugate acid is. A conjugate acid is formed when a base accepts a proton (H+). In the case of hydrogen sulfide (H2S), when it accepts an additional proton, it transforms into H3S+. This species carries a positive charge due to the extra proton.
In summary, when H2S acts as a base and accepts a proton, it becomes H3S+, thereby making it the conjugate acid of H2S.