Leave your native country and go to the land I will show you - Genesis 12:1
God didn't give Abram a lot of details - Leave your lifelong home for the land I will show you
He promised Abram to be a father of a great nation and the entire earth would be blessed through him - Genesis 12:2-3
There had to have been questions:
Abram went without questioning God or asking for signs
He believed God enough to step out in obedience and helped bring the salvation we enjoy into the world