you cant get used one out and re-use it they tear up when you remove them unless their the ones with the nuts on them that bolt in,pull in types cant be re-used ,any parts store sells those in a pack of 4 or most tire shops will give you one if you ask them for it,good luck
In tubeless tyres the valve is fitted to the wheel rim itself, so you can remove the valve and replace it with a new one in order to re-use the wheel. Tyres or wheels that have an inner tube fitted don't have the valve on the wheel itself it is connected to the inner tube, and can be easily removed you just put a new inner tube in. If you just want to take the valve out and use that, you would be better off buying a new one because they are not expensive. If you have no choice then you will only be able to re-use a valve from a tubeless tyre as the other type has the vale permanently attached the inner tube. To remove the valve from a wheel rim you need to first take the tyre off (usually with the help of a machine, as they can be quite tough) and then push the valve out off the hole from the back as there is a lip and is difficult to do it from the other way then just refit the tyre.
Just buy a new one for goodness sake!!!
