For the first equation:
3H1 + 3He2 = 3He2 + 1n0
Therefore, the missing particle is 0n1 (neutron).
Answer: 0n1

For the second equation:
2H1 + 1H1 = 3He2 + 4He2
Therefore, the missing particle is 0n1 (neutron).
Answer: 0n1

For the third equation:
238U92 + 8n1 = 246Es99 + 6 1n0
Therefore, the missing particle is 1n0 (neutron).
Answer: 8n1