They are generally solitary animals, meaning that all the molehills in a small garden can be the work of just one mole.
The molehills are a result of it/them excavating a network of underground tunnels and chambers in search of its/their staple food, earthworms.
People have been known to collect this soil from farmers fields and public areas.
You will be well advised to refrain from this practice as it is against the law.
Apart from tresspass you could also be charged with theft!
If the molehills appear on the lawn, remove them as described above and sweep the surplus soil off with a stiff broom / brush.
There are a number of devices available to control them, such as noise emitting types that are said to drive them away, and the more common traps that kill the mole.
There are also types that capture them alive for release elsewhere, but sometimes in the long term, it is better to just employ the services of a mole catcher.
Animal urine is reputed to be a good deterrent so having a pet cat or dog, may help.
The use of poisons is strictly regulated and you should seek advice from your local council’s environmental department before using this option.