< Put score in custom data >

Hi, 
First, sorry for the bad english, I'm French !
So here's my problem, I will go as stage to understand better :

You fish (custom datapack of a lot a fish) and get an egg everytime
The egg is instantly clear and you get a score of 1 wich detect where you are to know what type of fish you could have
It roll the fish you get, his stats (age, weight and therefor price)
It put all that info in the lore of the fish

Now I want to be able to sell this fish, but for that, I need to have his price, for that I need to have the price in the data of the fish, or maybe get it from the lore (but i don't think you can).
So here I am, not understanding how to put the custom data score on the fish, after that I will know how to get the data and put it on a scoreboard... Thanks in advance ! 🔨
(Minecraft Java 1.21)