I have a similar situation where I have users, I have accounts and I have roles. You can simply swap out Account with Organization.

The roles migration ...

class CreateRolesTable extends Migration
{
 
    public function up()
    {
        Schema::create('roles', function (Blueprint $table)
        {
            $table->increments('id');
            $table->string('name');
        });
    }
 
    public function down()
    {
        Schema::drop('roles');
    }
 
}

The migration that creates the pivot table ...

class CreateRoleUserAccountTable extends Migration
{
 
    public function up()
    {
        Schema::create('role_user_account', function (Blueprint $table)
        {
            $table->integer('role_id')->unsigned();
            $table->integer('user_id')->unsigned();
            $table->integer('account_id')->unsigned();
            $table->timestamps();
            $table->unique(['account_id', 'user_id']); // This ensures that a user can have only ONE role per account
            $table->foreign('account_id')->references('id')->on('accounts')->onDelete('cascade')->onUpdate('cascade');
            $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade')->onUpdate('cascade');
            $table->foreign('role_id')->references('id')->on('roles')->onDelete('cascade')->onUpdate('cascade');
        });
    }
 
    public function down()
    {
        Schema::drop('role_user_account');
    }
 
}

User model ...

    // Determine which role a user has for a specific account
    public function AccountRole($account_id)
    {
        return $this->belongsToMany('Role', 'role_user_account', 'user_id', 'role_id')->wherePivot('account_id', $account_id)->withTimestamps()->first();
    }
 
    // Fetch all of the accounts/roles for this user
    public function AccountRoles()
    {
        return $this->belongsToMany('Role', 'role_user_account', 'user_id', 'role_id')->withPivot('account_id')->withTimestamps();
    }
 
    // Fetch all the accounts for which this user is an Admin (note that the admin role is the first record in the roles table id=1)
    public function AdminAccounts()
    {
        return $this->belongsToMany('Account', 'role_user_account')->wherePivot('user_id', $this->id)->wherePivot('role_id', 1)->withTimestamps();
    }

Account model ...

    public function AccountUsers()
    {
        return $this->belongsToMany('User', 'role_user_account', 'account_id', 'user_id')->withTimestamps();
    }