Ok so in the solar cave or whatever it's called...what are the keys you..

They should be scattered throughout the floors of the dungeon. I believe the HMs you'll come across in any manner in the Solar Cave are Surf, Waterfall, and Dive.

The keys are scattered throughout Solar Cave randomly-a good way to make sure you get them is to use X-Ray Specs or a Scanner Orb to show you where all the items are on each floor. If you do, you should be able to get the 2 you need, but remember, you can go back and keep getting keys so if you only have one when you need it, use it, then look for more and come back with one already in your bag, or something like that. You'll need the keys for the 10th Floor-Link Cable (for trade evolutions), another for the 15th Floor, where HM Waterfall is; look for the locked doors, they're not always easy to find (Again, this is where X-Ray Specs will help you). The other HM Surf, is on the 20th Floor (top floor), but you'll need to have a Pokemon leader who can either fly, walk on water, or go through walls to get to it. By the way-the keys are all the same. Any key will work on any lock, it's not specific, even if you got it through a Wonder Mail code or another dungeon!
Hope this gets to you ASAP!

Ok,
1)There just small silver keys. You'll know one when you see one.
2)You get them at the begining of the dungion (usually around the stairs)
3)there surf,waterfall,dive,and I think one other.If you go back after you get them there will be linkcable's in there places.

Ok I Can Put Three Steps To What Your Question Is
1) There Small Tiny Keys You Will Find Them if U Look everywhere At Every Single Room On Every Floor in Solar Cave
2) Yes There Are Hms
3) When U Use A Key On The Key Box Go Into Inventory Select Key And Then Hit A button On Use and It Opens The Lock!