As a previous owner of a Nikon PB-6 bellows unit, I remember from the manual that Nikon did recommend using macro lenses with the bellows unit. I don't see why a non-macro lens would not work with a bellows unit, but you will certainly be able to get even closer to your subject with a macro lens (if that matters for the type of macro shots you have planned). Also, macro lenses are usually specifically designed for close-up photography and will likely give you better results in this scenario.

An important issue to consider when using a bellows unit is the presence of an aperture ring on the lens. Unless the bellows unit specifically provides a feature to change the aperture on the lens (typically a lever close to where you mount the lens on the bellows unit), you will not be able to stop down the aperture on your lens. You really want to stop down the lens, because with a bellows unit, the depth-of-field (DOF) of a wide-open lens will be tiny.

To be on the safe side, I would choose a lens with a dedicated aperture ring, allowing you to set the aperture manually. It can be a manual focus lens or an autofocus lens, just the aperture ring needs to be there. Nikon "G" series AF-S lenses do not have an aperture ring like the older "D" series AF/AF-S lenses do.

I was using an older 60 mm AF-D Nikkor micro lens with my bellows, but I also had the 70-180 mm Nikkor micro zoom lens mounted on it. With the larger focal lengths, you get higher magnification. It really depends on your intentions.

Any mountable lens will work just fine on your bellows, provided you can change the aperture somehow. But since you have a Nikon bellows unit, I would go for a used Nikon manual focus micro lens (50 mm or longer), they should be available for a reasonable price and they are all equipped with an aperture ring.