NiMeshParticleSystem and NiMeshPSysData cannot be made directly

[NoBarkNoBiteNoonan]

You cannot create either NiMeshParticleSystem or NiMeshPSysData with the Insert Block menu directly; they do not appear in any of the lists and require you to convert a NiParticleSystem or NiPSysData, respectively, to create them in a file.