where is the best site to download gmod10

Only place.

u cant download gmod10 off the steam store page just regular gmod

Gmod 10 = Regular Gmod

It’s just another name for it.

If it was the free one you wanted, that’s Gmod 9. However, it’s not supported anymore. It’s best to just get Gmod 10/Gmod

That’s the point. Once you purchase Garry’s Mod off of Steam, it will automatically be available for you to install in the Library tab.

If you are referring to the old gmod that utilizes the classical source engine, it does not exist anymore.
You cannot legally download it anywhere