How many neutrons are in ni?

It depends on the isotope. The most common naturally occurring isotope is 58Ni. Ni has the atomic number 28, so there are 30 neutrons in that isotope. There are four other stable naturally occurring isotopes with atomic weight 60, 61, 62 and 64. There are also around twenty unstable and radio-isotopes with atomic weights ranging from 48 to 78.