Django: How to use and return 2 values from a model

I have 3 tables, a relation many to many. 1 is INVOICE 1 Product(as category) and the middle one who links them. I need in the middle table to get also the "price" from product table not only the name; because i have an inline form and when i select the product name i would like the price to appear without the user to type it in. Can someone help ?

my email so i can send the code: tosadenisandrei@gmail.com

#models.py

    class Product(models.Model):
 
    
        category = (
            ('Choose category', 'Choose category'),
            ('Small parts', 'Small parts'),
            ('Big parts', 'Big parts'),
            ('Material', 'Material'),
            ('Wheels', 'Wheels')
        )
    
        category = models.CharField(max_length=20, choices=category, default='Choose category')
        product_name = models.CharField(max_length=30)
    
    
        rate = models.DecimalField(default=0, max_digits=10, decimal_places=2)
        net_amount = models.DecimalField(default=0, max_digits=10, decimal_places=2)
        gross_amount = models.DecimalField(default=0, max_digits=10, decimal_places=2)
    
        # tax = models.DecimalField(default=0, max_digits=10, decimal_places=2)
        # commission = models.IntegerField(default=0)
        bar_code = models.CharField(max_length=40, default='')
    
        description = models.CharField(max_length=200)
    
        # @property
        # def get_special_combination_value(self):
        #     return '{}{}'.format(self.product_name, self.rate)
    
        def __str__(self):
            return self.product_name


    class ProductTry(models.Model):
        type = (('item', 'Item'),
                ('service', 'Service')
                )
    
        product = models.ForeignKey(Product, blank=True, null=True, on_delete=models.CASCADE)
        invoice_id = models.ForeignKey(Invoice, blank=True, null=True, on_delete=models.CASCADE)
        measurements_selling = models.CharField(max_length=50, default='item', choices=type, null=False)
        quantity = models.DecimalField(max_digits=10, decimal_places=2)
        # formular_price = models.ForeignKey(Product.rate, blank=True, null=True, on_delete=models.CASCADE)