lle parcio is a parking space/place.
maes parcio is a car park or parking lot.
lle parcio gwag or gwagle parcio could be used if you are hunting for an empty parking spot/slot/bay/space.
In Welsh, lle can mean 'a space', 'one space, or 'some space'. The same with any noun, as there is no indefinite article 'a' in Welsh.
As with many languages, there is not always an exact one-to-one match between the range of meaning of a particular Welsh word or phrase and a given English one.