Well if they’re separate fixtures you’ll need to have or you’ll install the junction box behind each fixture location……and locate and extend the wiring to these locations…
Some fixtures have a recessed 1″ space within the mounting plate….allowing the short surface mounted box to be used for the connections…….Others with flat mounts may need a flush/recessed j-box installed IN the wall ……hung from the drywall/plaster using a Remodel box)……it’s harder to attach to the stud unless the wall is wide open…….