I tried but I can't set the price of the package and above all I don't have the possibility to choose the package in the point of sale.
Unless I do it wrong

I see what you are saying, a package can have its own barcode would you know if a package is added to an order by scanning barcode?

For price you can define a promotion or in pricelist

The other possible options which largely depends the inventory management of these products/ packs are
a. Define pack as Product variant, you can provide additional price
b. Define the package as an independent product