I found a 1942 nickel with no mint Mark is this right?

Yes. Nickels made at Philadelphia did not start using the P until 1980. From 1942 - 1945, the silver 'war nickels' did use the P, above the dome of Monticello, and the D and S were placed there as well just for that short period. However, non-silver nickels were made at Philadelphia and Denver in 1942. On these, the D is in the customary spot to the right of Monticello, and the Philadelphia has no mint mark. For 1942 only, no silver nickels were struck at Denver, so you won't find any with the large D. On other D and S nickels, the mint mark was moved to the front starting in 1968.