You want to know the scale of what?
Using your numbers:

Characters can march 5 tiles per day on average but as you said, crossing a mountain should take more time.
Distances for one day on a flat terrain, with a road, is 40 miles, or 65 km if you live outside the USA/Myanmar.
65/5= 13 km. Using your numbers, each tile is 13 km across.

Here's a reference to help you: https://www.cartographersguild.com/s...ad.php?t=19730
As I understand, a day of travel on horse is about the same as on foot. Horses can go faster in burst but they will eventually get tired just like humans.

So for drawing the map I need a scale that fit this description and have difficulties finding it.
How to draw "moutains" where heroe can go, distinguish them from impassables ridges, and all without covering the entire map of moutains.
I assume there can be only one element per tile? Put a bigger mountain for the impassable terrain and smaller ones with passable but difficult terrain. They could also features valleys.