There is none, it’s a combination of distance to runway and your current altitude, i.e. the higher you are the earlier you want to start your descent. You’re also looking for a nice steady descent rate at a constant speed.
You can use more power to reduce your descent rate, less power will increase your descent rate.
If you start your descent too late, i.e. too close to the runway then you’re going to have problems keeping control of the speed.
Make use of the PAPI lights at the end of the runway, see How PAPI Lights Work | Boldmethod
Just practice and you’ll get a feel for it, and the good thing about the simulator is you’re not going to kill yourself learning.