3rd Gen Ivs?

how do you tell the pokemons iv number?

I don't think you can...it's a predetermined value when you run into a pokey/capture a pokey. The IV value never changes once it's set on a pokey which is almost the almost you run into it. If you're looking for an IV of 0, you'll know if it has 0 IV if you can get to Mirage Island. Check GameFaqs.com for more info.

I never heard of an Iv before. :\

So I just have to hope it's number is 0...

Their Individual Values.
It has something to do with the highest stats that your pokemon can get.
The highest stats are based on:
Base Stats
Indiviual Values
Effort Values
And maybe something else.
So people who put research into the game (or are just really lucky) can get the strongest pokemon.

the chance of getting a EV 15-15-15-15-15 is equal to 15^5... so calculate the chance of that? In gameboy, this is impossible however online battling you get to adjust your IV so that you can use hidden power.

There is a method for calculating the IV's of your pokemon, but you must do it as soon as you catch them(if you use them at all it will be inaccurate).

I can't remember the exact formulae, but I think I found it on gameFAQs.com. Before you calculate them, you save the game. You then use alot of rare candies(this way you get them to a more accurate level without giving them any effort values). You then use the formulae to calculate IV's, it's just a pity I don't remember the actual formulae.

Stat = ((BS * 2 + IV + EV/4) * L/100 + 5) * P

where BS is base stat, IV is individual value, EV is effort value, L is level and P is the effect that personality has(either 1, 1.1 or 0.9).

Hit Points = (BS * 2 + IV + EV/4) * L/100 + 10 + L

where BS is base stat, IV is individual value, EV is effort value and L is level.