You potentially will get a lot of different answers here, just like the web. The simplest answer is pick any one pitched at a beginner level such as from https://connect.garmin.com/modern/explore/training-plan. No beginner's plan will be hugely wrong, the main thing is to follow it and you will complete. If you have difficulty choosing between many, remember you are looking for sufficient (of which there are many) not perfect (which is unknown).
Yeah, what the others said. At the end of a 5 km I have never been able to get more than 95% so in the absence of any other information you could go by what you have seen in a 5 km and add a few beats rather than a formula that may be true for populations but not any one person. Kinda like you would never by a pair of size 8 trainers and hope they would fit on the basis that the average is say size 8 +-2.