If you want to directly exchange the stock fans these are what I used: Noctua 40mm 12v fan for the motherboard and exhaust fans. You’ll also need this step down converter because they are 12v fans instead of 24v but they work well and are nice and quiet. I also keep the exhaust fan turned off all the time unless printing with ABS. Even with a noctua fan replacement in there it’s just so loud because its in a huge echo chamber. For the extruder fan I used this 30mm 12v fan and again used the step down board to reduce the voltage to 12v. There’s plenty of extra room in the extruder head to fit it in there and I haven’t had any cooling problems since installing it.