Recreational / Hobbyist UAS pilot reported flying in controlled airspace without authorization.

Narrative

I was invited to fun fly my DJI Mini Pro 4 on a friend's property located in an industrial park in Location X. I flew the drone on that property twice over a span of two days; roughly an hour and a half each time on Day 0 and Day 1; thinking that my drone was legal to fly without authorization because it is less than 250 grams.After flying there on both occasions; I was sharing my experience with a different friend who flies RC aircraft and is also involved with the local RC flying field. He alerted me that my drone might not have been legal to fly without authorization depending on the DJI 'Fly More' package I'd purchased and where I was flying. I usually fly my drone around my farmstead far away from everything in Class G airspace; so while I thought I was prepared to fly in Location X because of the specific model and my misunderstanding with the regs governing it; I was not.My RC-savvy friend and I looked it up and I believe he is correct. My drone does not appear to be legal to fly due to a heavier batteries that come with the longer flight version of the 'Fly More' package that was available two years ago; when I purchased the drone.Also; after reviewing the latest regulations more carefully; especially as they apply to my drone (lots of online message boards; YouTube videos and the FAA site); I now believe I was indeed required to obtain prior authorization regardless of the weight; considering the private property I was flying over is inside the inner ring of Class C Airspace. I'm not sure how I completely missed or misunderstand so much about how the regulations apply to my specific drone; since I made the entire decision to purchase this specific drone based on considerable research prior to my purchasing it two years ago.As soon as I learned of my mistake; I took immediate action by way of the following steps to avoid this in the future:1. I re-reviewed the regulations with the help of my RC friend to gain an better understanding of what is expected of me when I fly my drone. 2. I took the Part 107 Small UAS Initial Training Course for Part 61 Pilots; passed the test and filled out the application for my Part 107 certificate. I met with my CFI II flight instructor to review the mistakes I'd made; the action I'm taking and also to complete the process. I now have a 'temporary' paper Remote Pilot certificate. 3. I also researched how to obtain clearance when within controlled airspace. From this research I located and downloaded the 'Aloft' app and have familiarized myself with its use. 4. I intend to continue with more online training regarding UAS operations and regulations until I feel my knowledge and processes are up to par with where I am with my private pilot knowledge base.