en_tn/gen/15/06.md

he counted it to him as righteousness

"Yahweh counted Abram's belief as righteousness" or "Yahweh considered Abram righteous because Abram believed him"

I am Yahweh that brought you out of Ur

Yahweh was reminding Abraham of what he had already done so that Abraham would know that Yahweh had the power to give Abram what he promised him.

to inherit it

This can be translated as "to receive it" or "so that you will possess it."

how will I know

Abram was asking for more proof that Yahweh would give him the land.