To determine the number of elements that show a 6 oxidation state among Th, U, Np, Pu, Am, Cm, Bk, Cf, Es, and Fm, we need to analyze the electronic configurations and oxidation states of these elements.

1. Thorium (Th)
Th has an atomic number of 90 and its electronic configuration is [Rn] 6d^2 7s^2. The highest possible oxidation state for Th is +4 in compounds such as ThO2.

2. Uranium (U)
U has an atomic number of 92 and its electronic configuration is [Rn] 5f^3 6d^1 7s^2. Uranium can exhibit various oxidation states, including +3, +4, +5, and +6. The +6 oxidation state is commonly observed in compounds such as uranium hexafluoride (UF6).

3. Neptunium (Np)
Np has an atomic number of 93 and its electronic configuration is [Rn] 5f^4 6d^1 7s^2. Neptunium can also show multiple oxidation states, including +3, +4, +5, +6, and +7. The +6 oxidation state can be found in compounds like NpO2.

4. Plutonium (Pu)
Pu has an atomic number of 94 and its electronic configuration is [Rn] 5f^6 7s^2. Plutonium can display oxidation states ranging from +3 to +7. The +6 oxidation state is observed in compounds like PuF6.

5. Americium (Am)
Am has an atomic number of 95 and its electronic configuration is [Rn] 5f^7 7s^2. Americium can exhibit oxidation states from +2 to +7. However, the +6 oxidation state is not commonly observed for Am.

6. Curium (Cm)
Cm has an atomic number of 96 and its electronic configuration is [Rn] 5f^7 6d^1 7s^2. Curium can display oxidation states from +3 to +8. The +6 oxidation state is not commonly observed for Cm.

7. Berkelium (Bk)
Bk has an atomic number of 97 and its electronic configuration is [Rn] 5f^9 7s^2. Berkelium can exhibit oxidation states from +3 to +7. However, the +6 oxidation state is not commonly observed for Bk.

8. Californium (Cf)
Cf has an atomic number of 98 and its electronic configuration is [Rn] 5f^10 7s^2. Californium can display oxidation states from +2 to +7. However, the +6 oxidation state is not commonly observed for Cf.

9. Einsteinium (Es)
Es has an atomic number of 99 and its electronic configuration is [Rn] 5f^11 7s^2. Einsteinium can exhibit oxidation states from +2 to +7. However, the +