How do i do to make a bonus drop by mining my ore with fortune ?

Add loot table for your ore block

Sorry im a day late, but here is how:

First,create a loot table with whatever name, the actual name isn't important
Next, o inside, and change the top line to blocks/ then the ore name. When doing the ore name replace capital letters with a non-capital and a _ (example: RetroDiamondOre would become retro_diamond_ore, NoobOre would become noob_ore, etc)
Next, make sure the middle section (dropdown) is set to mod and the bottom dropdown is set to blocks
Then modify the existing loot table to be a loot table with 1 rolls (mix and max, no bonus rolls)
Add the gem u want it to drop, set min and max to 1, and click the "affected by fortune" enchant.

Now go to your item, go to its drops area, and click the box for "using a loot table"

If you want to it drop itself with silk touch, do the next 2 steps
Go back to the loot table, go to the group down that says Ignore silk touch, and change that to "Only Without Silk Touch"
Create another entry of the same, but change the gem for the ore, make sure Affected by Fortune is off, and that the dropdown is set to "Only With Silk Touch"