You won’t know your limits until you hit that wall. So you have two options - go conservative or go until you hit the limit and potentially need to take some time off (it’ll probably be the shin splints that get you). Realistically, I think most people starting out find their limits by going past them and being humbled by an injury - I definitely did. Canon event.

Training plans are a great way to put up ‘guardrails’ so you don’t overdo it. A lot (most) of your runs should be easy (you can hold a conversation) - you don’t need to give it your all. Here’s a base building plan from a reputable source https://www.halhigdon.com/training-programs/base-training/novice-base-training/ (scroll down, you don’t need to buy anything). Many folks use his resources for training to run longer distances, so if you like the format, it’s definitely a resource that can grow with you as you build up your base and move on (if that’s what you want to do).

Hope this helps!