There are tonnes of different ID's within Facebook business manager. This tutorial will show you where to find the Ad Account ID.
In Business Manager do the following:
- In the top left hand corner is a hamburger menu, click on that to display a drop down
- In the bottom of the drop down is a small link which says "All Tools", click on that
- This will open a "mega menu". Look to the column with "Settings" and click the "Settings" option
- This will then display the business setting for the ad account where you can find the Ad account ID