From reading http://en.wikipedia.org/wiki/Helium-3#Fusion_reactions, the 2p are two protons, and not positrons, as valarauca1 is saying.

So, 4 protons and 2 neutrons go in, 4 protons and 2 neutrons come out.

But charge still needs to be conserved -- I presume that the spare electrons just aren't shown in the reaction; if they were bound to the protons, then we'd see 2H rather than 2p.