Although Pathfinder and 3.5e are very similar since Pathfinder was made to be a better 3.5e, they are still two different systems. You usually can’t just take stuff from 3.5e and put it into Pathfinder, you need to convert it and change it. A lot of rules and subsystems have been changed, too much for me to go into in a comment. I would do some more research on it, but I would still suggest just sticking with Pathfinder.