Helicopter Pilot reported an airspace incursion occurred when they flew through Class D airspace thinking it was Class E.

Narrative

I had accepted a late shift interfacility transfer flight. After doing a quick flight/ time planning I determined that I could complete the flight within my 14 hours; but extending beyond my 12 hour shift. We picked up at facility in ZZZ1 and dropping off in ZZZ. This is an area that this base does not frequently cover and an area that I have never flown through. During the flight to ZZZ1 I was looking over my route and entering necessary enroute frequencies into the radio que. As I was looking over ZZZ; I had noticed the class E to the surface are extending to the northeast. With how Foreflight was set up and how a shaded barrier was overlaying the dashed blue line of the class D; I had determined on the fly; that the airspace was class E to the surface. This was while in flight. Thinking it was class E to the surface; I zoomed in and entered the UNICOM frequency and was broadcasting on it. I flew in; dropped the patient at the hospital and flew back out. After I got back to base; Company called me and said that the ZZZ ATC wanted me to call them. I called them and explained what had happened. This was me not thoroughly looking over the airspace like I should have. I need to be absolutely sure of the airspace I fly into; especially in areas that I have never been. I am sure complacency played a part as most airspace in the area; aside from the ZZZ2 Class B are either Class C or Class D. I have never had an airspace violation before. I am also and instructor and this is something that I make sure my students know very well. This event had an impact on me and I am certain; something like this will not happen again. I need to slow down and absolutely flight plan without multitasking before I take off.