Obviously the RCAs would connect to the Pioneer’s pre-amp outputs (your picture is too small for me to see exactly where they are). You’ll have to get a pin-out diagram for the 9-pin adapter from Bose to determine which RCA is what (center, surround, etc.).Can get the 9 pin adapter with RCA plugs on the other end....but at a loss as to what output on the Pioneer I would attach to.
Is that the back of the subwoofer or the head unit? In my experience, Bose systems have proprietary connections designed to prevent use with other brands or generic AVR's. Unless they've changed strategies, the sub gets all audio signals from a head unit, then redistributes them to individual Acoustimass satellites via non-standard connectors. My system is pretty old, so yours may be different.Sorry-\
thought you got that from the initial comments. Attached photo shows the Bose input...it is the 9 pin DIN. Can get the 9 pin adapter with RCA plugs on the other end....but at a loss as to what output on the Pioneer I would attach to. I have had a Bose speaker system on this before, but not with a powered subwoofer.