The method of upgrading depends on where you purchased UVPackmaster 2:
Use the discount code uvpm2to3 when making a purchase – discount will be applied automatically. Note that the code will only work when you make a purchase from an account which already owns a UVPackmaster 2 PRO license.
Unfortunately, Gumroad does not provide an option for a universal discount code. Hence, you need to write to us directly at firstname.lastname@example.org in order to get your own code. Make sure you write to us from the email address you used to purchase UVPackmaster 2.