N.J. Stat. § 43:16A-11.6
A member who is a member of another State-administered retirement system or pension fund at the time of enrollment in the Police and Firemen's Retirement System and does not contribute to the other system or fund after that time may transfer the service credit in the other system or fund to the Police and Firemen's Retirement System upon application and transfer of the member's contributions from the other system or fund to the system. If the member has withdrawn the contributions to the other retirement system or pension fund, the member may purchase credit for the service in the other system or fund. The purchase shall be made in the same manner and be subject to the same terms and conditions provided for the purchase of previous membership service by section 1 of P.L. 1973, c.63 (C.43:16A-11.4).
N.J.S. § 43:16A-11.6