A Tower Controller reported they issued a vector to an aircraft that was below the Minimum Vectoring Altitude.

Narrative

I had two IFR airliners inbound. I believe Aircraft Y followed by Aircraft Z. I had a VFR aircraft doing full stop taxi backs. It was a Boeing 737. I departed the aircraft and while he was on the crosswind or turning downwind. I did point outs to each sector and coordinated him to go after Aircraft Y on final. Approach approved. On downwind I got slightly distracted about a short conversation as the pilot recognized my voice. I turned his base to follow Aircraft Z. I saw the Bonanza around Location X which is a very typical location for VFR inbounds and I incorrectly assumed he was VFR. He was actually an IFR on Visual Approach. At some point apporoach called about something. I remember him saying I had him' and the call ended. I assumed approach was going to tell me he was on a 120 assigned heading. I can't remember if it was before or after I turned the Bonanza. I turned him slightly to parallel final to follow Aircraft Y (probably under the MVA). I then turned him towards the Aircraft Z to base him. I probably didn't turn him enough and I think I turned him an extra 20 degrees or so to go behind. I issued traffic and got him in sight the. Switched him to Runway XXR. It wasn't until he was about a 3 mile final I saw his tag and he was IFR. That's when I realized approach was probably going to tell me he was IFR. So I had him confirm Runway XXR was in sight and cleared him for the Visual Approach to Runway XXR It was a 100% example of expectation bias."