We propose and demonstrate simultaneous multiple dense wavelength division multiplexing (DWDM) channels optoelectronic non-return-to-zero (NRZ) to return-to-zero (RZ) regenerative format conversions based on a single phase modulator (PM) and a fibre delay-interferometer (DI). The PM is driven by a local RF clock signal, and the DI with free spectral range (FSR) equals to the channel spacing is used to extract the chirps induced by the phase modulation, for all the channels at the same time. Since the original carriers are suppressed to some extent while the chirps are extracted, thus the NRZ-to-RZ conversions can be achieved with regeneration. The proposed multi-channels format conversions are successfully demonstrated at 16*10 Gb/s, with channel spacing of 100GHz. Bit error ratio (BER) measurements show 3.5 and 4.2 dB penalty improvements for 50 and 75 km transmission without dispersion compensation, respectively.