This entire question confuses me (how can you know the Hidden Power type/base stat but not know the IVs?), but I'll try my best to answer this anyway. Not sure which question you want answered, so I'll answer both to the best of my ability.
By the way, if all you want to know is what your Suicune's potential IVs are based on the fact it has Hidden Power Electric with base 70, you don't need to know what percentage of the IVs is included at level 40. Level doesn't affect IVs (outside of stat calculation), thus it doesn't affect Hidden Power.
"What are the stats of a wild lv 40 suicune if it had hidden hp elct power 70?"
If you're talking about actual stats, I need more information to answer that. Just the level and Hidden Power is nowhere near enough. All it gives me is a rough idea of what the stats would look like based on the level, and a few possibilities for IVs. Given how you can you go look up your Pokemon's stats in-game in two seconds, however, I'll assume you're actually talking about IVs, not stats. In that case...
If you're correct in saying Suicune's Hidden Power is base 70 Electric, here are the possibilities for its IVs (HP/Atk/Def/SAtk/SDef/Spd):
As mentioned in the existing answer, level doesn't affect the actual IV values, but it does affect how many of them are added to the total. So at level 100, you'll have all the IV points on your Pokemon, but if it's not level 100, not all of them are included. This is caused by the stat formulas below, which multiply IVs along with base stats and EVs by the Pokemon's level. The lower the level, the lower the result, the lower the effect from base stats, IVs and EVs is.
As you'll notice, HP's formula is a bit different - there's an extra 100 added at one point - which is why you'll notice the HP stat always appears to be bigger than the others.
If you want me to calculate your Suicune's stats based on those formulas, I'll need Suicune's Nature and each stat's EVs. Although, as mentioned before, I don't know why you'd need me to do that when you can go look it up in your game.
Source for IVs based on Hidden Power
what percentage of personality values is used at lv 40
Once again, I'm going to assume you're talking about IVs, not personality values. PVs have nothing to do with a Pokemon's level or Hidden Power for that matter. PVs determine gender, shiny Pokemon and other things, while IVs are the points from 0-31 I've been talking about this whole time.
As mentioned, you don't need to know the answer to this to know your Pokemon's IVs (level doesn't change the actual IV value outside of stat calculation), but I'll answer this anyway in case anyone's curious.
The answer, quite simply, is the Pokemon's level in percentage form. That means that 40% of Suicune's IVs are being put to use in its stat total, because it is level 40.
What I did was took the stat formula, and assumed that the value of "base" (the stat's base e.g. Suicune's base Special Attack is 90) was 0 and assumed that Suicune had no EVs. (Obviously the base stats aren't all 0, I only did it that way for simplicity's sake.) Then I added "31" in place of "IV" in the formula. The result I got was 17.4. If I remove the extra 5 added in the formula, this becomes 12.4. Since it is impossible for the base stats and EVs to have made a difference to the result, since they're both at 0, the 12.4 was created solely based on IVs (or, in other words, Suicune's entire stat is made up of points it got from its IVs in its respective stat).
Simply put, this means that 12.4 of 31 IVs were included in the stat total. If I convert that to a percentage, I'd get 40% - the same as Suicune's level. You can confirm this is correct by multiplying 31 by 0.4, which gives you 12.4 like it should. I experimented and changed the IV value to different numbers; still, I kept repeatedly getting 40% regardless of what IV value was entered.
To clarify that base stats and EVs don't affect this (they shouldn't), I tested this out by determining the Special Attack of a Suicune with 31 IVs, 252 EVs and a neutral nature in Special Attack, with its base 90 in that stat also included. The result was 114.6, with the extra 5 in the formula included. If base stats and EVs don't affect the percentage of IVs added to the stat total, if I were to make Suicune's IVs 0 (effectively removing them from the formula), then the result of that would have to be the same as 114.6 − 12.4, yes?
114.6 − 12.4 = 102.2
Both result in 102.2, so this answer is correct. 40% of a level 40 Pokemon's IVs are included in its stats. This answer is identical for HP, since the extra 100 doesn't affect IVs. This exact same rule would apply to base stats and EVs, since they're both treated the same way in the formula.
Technically it would be slightly lower than 40% in this case, since the game gets rid of the 0.2, but that's besides the point.