converting NavMesh to normal mesh?

i'm trying to use A* Astar pathfinding and want to use the "Navemesh Graph".

the problem is that i'm fairly new and i have no idea how to build my own mesh.

triedusing blender as it's suggest in this documentation but with no luck.

another solution i've found is convert unity's NavMesh to normal mesh which is what i prefer since you don't need to rebuild/export your scene to blender.

my problem now is all that i've found information about this subject is 6-8 years old information that i have no idea how to use. example

so now my question is "is there an easy way to convert navmesh to normal mesh?"