Use a strange filter to your weapon to make it strange and see how many enemies you have killed on a specific map. TF2 strange filter is a one action item that allows players to upgrade weapons from default to strange.
Your weapon is tied to a specific map, and shows your killing statistic on this map. Also, your strange weapon has a prefix of this map in the name.
Visit DMarket if you want to buy or sell a TF2 Strange Filter.