Eloquent Relationship Pivot Table with 3 Model

Hi comunity... i'm a little confused, i need to implements a user role according to an trade unions that the user belongs. The user can belongs to a lot of trade unions but his role can be different.

The migrations will be:

users

• id
• name

roles -id -name

tradeunions -id -name

user_rol_trade

• user_id
• role_id
• trade_id

What would be the best way to do it? I've worked with pivot table with two models, but with three, I'm a bit confused Thanks a lot !