Hi @thines
You would want to add two server connects in the App Structure to retrieve the information from table 2 and table 3.
In your table 1 form, you would want to add a select box for the table 2 data and another one for the table 3 data.
In the properties for the select box, you would click on the trash can to remove the default options and then click on the lightning bolt to select the data source you created earlier. After that, you would select the lightning bolt to choose the text option and then the value field.
Here’s a tutorial on it, Dynamic Select Menu