If you want other ores to take a few more hits depending on the pickaxe, make it so if its a weak one (like the wood one) give it a tag. For example,
(This would be for the coal maybe?)
Give the wooden pickaxe the tag wood for this to work.
When this is created
Repeat every 0.0167 seconds
If this is colliding with tag: wood
Destroy this actor
Now after the "destroy this actor" it would make a duplicate version of it. That one would have a small change to it. If you want it to take a bunch of hits before breaking, make it create another stone blueprint with the same code. (Not the same blueprint of course cause that would cause it to never break) and do that a few times and ya r done! Now for a diamond pickaxe, you would have to make the blueprint make a DIFFRENT actor. So basically all of this 1 time or 2 times depending on the type of ore. Here are the tags I recommend using for it
Wooden pickaxe: #wood
Stone pickaxe: #stone
Gold: #gold
Iron pickaxe: #iron
Diamond pickaxe: